If SD only was there 4dys a month, I'd say leave her hair alone. Being she's with you 50% and her hair needs attention at least twice a day for 1/2 the month, I can see why the hair is under discussion in your home.

Being it's thick and curly, I'd take her to a good salon and consult as to what you'd still be dealing with after a cut (it's still going to be thick and curly) and do a computer view of what SD would look like with this or that cut. You also should consult on what shampoo/condition and perhaps detangler would best suit SD's hair.

Ask the child their opinion, then have DH discuss it with the mom. To cut a girl's hair any significant amount is a big deal emotionally and socially, and the child's wishes should be considered. As a BM and a SM, I think that the hair is just a symptom of a bigger issue. Maybe try to deal with the root of the problem first?

I cut out a rats nest out of SD hair and BM was angry because a piece of hair wouldn't stay up for BM wedding. I would def consult BM.

SD7 had the same problem, but she had straight hair. She's just so... Active, that it got knots in it. Her mother refused to get it cut.
It got to the point that SO and I asked if SD wanted us to get MIL to cut her hair. Not short, just above the shoulders. SD wanted it desperately, but BM kicks up a fuss about MIL cutting SD's hair because she's not a professional. Honestly, who cares? She's good, and she doesn't charge. I let her cut my hair.
Anyway, SO was CP and had just as much right to get her hair cut as BM. So just before she left for visitation with BM, we told her that when she got back, Nanna was going to cut her hair.
When she got back, her hair was cut to her shoulders and her fringe was butchered. BM was so pissed off that MIL was going to cut SD's hair, she took her to one of those cheap, crappy walk-in places, just to keep the power. Her fringe looked crap when it got done, so BM did an equally crappy job of trying to fix it.
The problem? SD still has trouble brushing her hair. Because SO was CP for most of her life, and he has short hair, he didn't teach her the right way to brush her hair. SD now does it in a way that makes her arm hurt after two minutes. It doesn't help that SD is always acting in a way that messes up her hair, and is just generally lazy in regards to hair care.

Anyway. Advice. My advice is dependent upon your circumstances. Does your SO have primary care, 50/50, or visitation? If it's one of the first two, then I'd say he has just as much right to make decisions as BM, and if it's that much of a problem, and SD wants to do it, then if I were him, I'd get it done- though I don't know if I'd go quite that short, even if SD wanted it. I'd maybe go with chin length if she really wants it short. Compromise between ear length and shoulder length.

If he just has visitation, it's a little bit trickier. Unless there's something in the CO that gives him the power to make choices like that, there's not much he can do. Except send BM a text or email saying tht SD has trouble brushing her hair, she really wants it cut, and if BM doesn't want to do it on her time, he'd like to make an appointment on his time. It's important to SD, and it would save time and be better for everyone.
The important thing is to text or email. Don't ask in person or over the phone. Documentation and all that.

If you can't get it cut, then I've got more advice. I used to have very long hair, and it's very thick. I'd get knots the size of bird nests overnight, and they took half an hour to brush out in the shower, with conditioner. BRAID OR PLAIT HER HAIR AT NIGHT. Use a good hair tie so it doesn't fall out. It worked wonders for me. If it gets messy during the day, like my SD's does, because I love her but she's a little twit when she plays, then do it during the day, too.

If it is kept long for religious reasons ... keep out of it.

But from the sounds of things it isn't and just a BM who hasn't a clue how to take care of her daughters hair.

I would let SO lead the path on this one. Sure, BM will get pissy and is SD able to stand up to her mother? After all, you aren't spending half your month with an angry BM.

I have thick wavy hair and spend time researching the best haircut for my hair. Layers can work... or not. You don't want it turning into a frizzball. Make sure you go to a good stylist and show her what SD wants and can she get it close to that.

If this is her first haircut maybe keep some of her hair for her mother to keep (some women are like that) But when you take her to the appointment, you talk to the stylist and discuss what SD wants and then leave on some errand. I would certainly leave the final decision to SO and make sure he pays for it.

As you are not married the BM could get really nasty and waste your time having you
personally accused of assault (trust me, it happens!). So I would leave this entirely up to SO. He has 50/50 with his daughters mother, not you. Just cover yourself legally as well.

My mom never cut my hair when I was little. It was probably down to my knees maybe? I know my pony tail was long enough I could still sit on it. My Dad said that if I couldn't take care of it I couldn't have it. He took me to have it cut to my shoulders. It was very freeing for me. No crazy long pony tail, pig tails or braids to deal with. it didn't take forever to get ready in the morning.

Cuntalotapus is all about what should be HER job but she never does it. I take SS and DS to get their hair cut. Or I'll buzz it. I'm pretty good with cutting their hair I learned it by practicing on my brother }:) I've given SS a mohawk but he didn't do anything with it so DH said no more mohawks.

I know hair is different for boys. I took my niece to get her hair cut and my sister was pissed. But she didn't want long hair and my sister wouldn't let her cut it. I was wrong and I know that but my niece STILL keeps her hair cut very short. it's an adorable look for her. I'm a little different. I have really long hair I just cut it from my waist up to the middle of my back. you know because that makes a big difference in the summer LOL

Devil's advocate because she's a girl and you have her 50% of the time, not full time. Let it go and find some products to help her. If this was a boy, maybe I would think that the BM might not flip out too much. But being that she is a girl and BM obviously likes her hair long, either discuss with BM and see if she agrees or let it go and get some products. If she was with you 100% of the time, I would say you get to make the decisions. But you have 50% custody, BM should also be on board. This is not to say that what you do in YOUR home is any of her business, but what you do that affects her in her home, yes, even if it is hair, will create WWIII.

Hair: People have problems with their hair all the time. And hair is a touchy subject for kids too. It's not as simple as people think.

Thanks to iamaSmom I now know I have 1b hair... Learned something new today!
However as a kid hair was a touchy subject for me: I am a red head and got teased for being adopted, being the helper of Satan, carrot top etc.
so I feel for kids and hair issues.

I hope this isn't a stupid question but when you say brush do you mean using an actual brush?

One of my nieces is biracial. She has sideshow bob hair. Seriously poor thing. Before I could keep her overnight my sister showed me how to do her hair. I had to spray some sort of olive oil stuff on her hair and then use a wide tooth comb. I separated her hair and started detangling from the bottom. It's a pretty lengthy job. But in the end it looks beautiful and I was able to french braid it.

I wouldn't take a 7 year old for a major haircut knowing that it would incense BM. An uncontroversial trim - yes, a significant restyle - no. Why cause all that conflict and put SD in the middle of it just because she has trouble brushing her hair? My 7 year old also has difficult curly hair but likes it long. I help her brush it out. When she's a year or 2 older it might become an issue but not at 7. I would try less confrontational approaches first: get a trim, get advice on taking care of her hair type, invest in products. DH could discuss it with BM to try to reach a mutual decision.

Speaking as a woman with thick, frizzy, curly hair...(thank you Irish and American indian blood)

Short hair is a great thing, it'll seem like it's back down to her rear end by the end of the month. I don't know why but it just grows so fast.

Anyway, use a detangler spray..I highly suggest agran oil as opposed to olive oil, mix it in a spray bottle with water or even 1/3 water/oil/ infusium leave in treatment, while still damp, comb with a wide tooth comb, and then braid it or put it in a top knot with those ouchless no metal parts hair ties. NO HEAT TREATMENTS EVER!!!!!!

Oddly enough to dry it fast, get one of those shamwow towels and wrap the braid or bun with it before putting it up. I swear it works as weird as it sounds.

I have very thick and curly hair. Believe me, it's not the kid'd fault; it takes bloody ages to brush. Instead of going drastic and cutting it off (and risking pissing off BM), would you.and SD consider getting her hair layered? It makes it so much more manageable. Oil and wide tooth combs are a curly haired girl's best friend.