Disconnect her phone service....wait for her to come out of the room, take the phone away. H can manage with her while you WFH, and then not sure from there but I wouldn't have let her in my home after all of her nastiness. 

I agree, if y'all pay for the phone and have the access to do it, shut it off. If not, at least take whatever phone chargers she has away. Most kids these days run around on 10% battery in my experience, so it won't be long before her phone dies.

Also, if you can do it without engaging with her physically, go ahead and take the door off the hinges. Whatever you do, do not go within 6 feet of her or raise your voices. Even if you're being recorded, you already know this child will lie and twist things to make herself look like a victim.

In my experience, the only option to send a kid away is an inpatient treatment center. They may decline to hold her if they determine she isn't actually a threat to herself or anyone else. Being a hysterical brat who tells lies for attention isn't going to be enough. And those correctional/military schools are extremely expensive and notoriously abusive so I wouldn't consider that an option either.

I'm sorry; it's a tough situation to be in. Your husband is between a rock and a hard place, it's untenable to have her at home, but there's nowhere for her to go if her mom won't take her...

Google "year round places for troubled teens". 

I'm so sorry you and your DH are dealing with this caca. {{hugs}}

I'm a social worker and have been through this with a previous client. Her grandparents had custody and the situation grew so extreme due to her behavior, they had to relinquish her into state custody. Nothing they did worked. Google "Immediate Placement for Troubled/Behavioral Teens" and your city/state. That is a place to start. Contact your local community mental health agency and ask for resources (they will have plenty). 

DH needs to ensure he has documentation from every "suicide attempt" (i.e. medical records, text messages, police reports, etc.) and all documentation of her behavior toward you both over the last few months. He needs to file an emergency motion to relinquish custody and provide that evidence. The courts can also involuntarily place her in a group home or behavioral health setting if neither parent can handle it. 

Isn't DH the NCP? If so, he is not obligated to take SD. He can turn down each and every parenting time. If BM is out of town, she needs to find alternative placement for her during vacation. If BM keeps kicking her out and SD reaches out, call CPS and the police for a welfare check. Let the police know that you cannot take her due to hostility and abuse toward you both. Let them and BM figure it out. SD being in your home is dangerous and needs to be avoided at all costs. This isn't just teenage angst. She needs serious intervention either for mental health or serious behavioral issues. 

Call DCF? Maybe tell them you're stuck and would like the state to step in and help (have her removed and placed into a facility) idk much about DCF but if you're calling asking for help- they must have resources at their fingertips and can see you are open and willing for a third party to step in. 

Oh no!  I would be very careful with her and trying to take physical things away. I'm guessing she'll react violently. Make sure that if you do, it's in a place where the cameras are.

You should at this point 100% disengage. Support your DH out of her earshot because it's clear she's also going to be coming after you.

I don't think you can commit her without BM's approval. Can you both instead, sit her down again, with the cameras, and tell her if she refuses to follow the basic household rules, so be it. You will both not help with anything. She does her own cooking, laundry and clean up. There will be no more discussions with her. She has to figure out her transportation to/from your home and make sure she can get to BMs (you'll drive her but you will not coordinate with BM and the time must work for you two as well, like any adult would do). You will not be helping her any longer (if she still trusts you this may be a blow but there are consequences to her behavior). She thinks she's so independent - then give it to her.  Meanwhile yes, DH starts the custody changes.

Are not alone with SD.   DH is the fool for taking SD in the first place, he's a fool thinking he had any control over SD.  Now it's his problem.   Just make plans for a place to go if DH is going to leave her with you.  
'As DH said he going to work, you are out of the house before him.  Pack a bag with yours needs so you can leave fast 

You need to back way off on getting involved in anything physical with this girl - honestly, you should not be directly involved with her at all. I get wanting to take her door off, but imagine how she could spin that to the authorities. Your DH was a fool to let her visit and there is no way that you should stay alone with her at all. (I wrote that before reading that Harry used the exact same word...) I know you want to help your DH, but you must protect yourself because it sounds like she is coming for you next.
I know you have said they have 50/50 - but often even with 50/50 one parent is designated as custodial, have you double checked the paperwork?
 

Particularly when they are a danger to themselves and any people of quality in the mix. Though these kids are far more often than not, toxic themselves and of dubious qualityu at best

Ship her off to experts who will both get her the help she needs, and hold her accountable to the point of her being a sobbing puddle of protoplasm when she pulls her bullshit.

Below are a few of a number of options to deal with ill behaved teen girls.  There are also co-ed and boy versions.  I would go with the all girls and only girls option with this POS SKid.

Though not  behaviorally motivated, my dad, me, my brother, and my SKid are products of Military Boarding School experiences.  All of us were either geographic/education or focus related.  None of us were in any trouble or a toxic influence on our familily.

I would say your SD is far beyond salvage for a Military School experience and would be hard pressed to get accepted.  She is in despirate need of a theraputic highly discipline focused isolated remote boarding school experience. Somewhere that will result in some very long cold or hot very thirsty miserable days and nights if she decides to run. I would not allow her in my life if I were you. At least not physically present in my life. Ship her ass off and nail BM for a shit pile of CS.  No need to bear the financial responsibility for BM's shit example and shit parenting solely from your marital income.

https://ashevilleacademy.com/behavioral-boarding-schools/

https://www.havenwoodacademy.org/disciplinary-schools-for-girls/

https://chapelhillacademy.net/

if she's going to cry "suicide" call for help. Even if you're 99.99% sure it's a manipulative lie, call and have her taken for a mental health hold? 

Who cares who pays for the phone, she is in your house and you guys are responsible for her. How do you know she won't use it to hurt herself (buy drugs to OD/call an adult boyfriend to pick her up so she can run away, etc.)

When SO's brother's kids were dropped off by both parents to SO and I, there were 2 and they were a lot like your SD. The options we looked into included something called a Therapeutic Boarding School. If you Google that term, you can see which ones are closest (or farthest lol) to your location. No way in hell can you live with this little monster. Also, no way she grows up to be anything other than a HCBM if she doesn't get under control. 

Does she have a key to BM's? He could drop her off there. Let BM know that SD is home and it's her choice to come home or not. I could be wrong, but I don't think anyone would balk at a 14 year old being left at their home alone. I realize it's not an ideal solution, but really at this point your DH only has bad options to choose from. 

Your SD sounds like my DH's youngest daughter (now 25) when she was your SD's age.  She called the cops on DH when she was 12 becasue, gasp!, he was trying to parent her by physcially taking her cell phone from her.  The little sh*t was taking photo's of our home and of me and sending them to her PASing mom and stepdad.  I said NO MORE!!  I will not tolerate this behaviour in my home.  I still shudder when I think about the hell DH's daughters and their mom and stepdad put me through. 

Some stepkids don't outgrow their meanness.  Take that as a precautionary warning.

My only suggestion to you is protect yourself, your sanity, your peace and your property. 

Stay out of this psychotic mess.  Let your DH handle all this B/S outside of your home.

Good luck.