About the strangers thing - i think it's normal. SD did this when she was like 4 & DH & I got married. I also corrected others to say I was her stepmother or before we were married, dads gf/fiance/etc.

Eventually we both kind of mutually tired of doing this & would just give an awkward smile to the stranger & then afterwards laugh about it.

About the other stuff? Your BF needs to handle her behavior issues.

People always assume my SD6 is my daughter too. We usually don't correct them. She's used to her BM's boyfriend being mistaken for her dad too.

Does your boyfriend step up and discipline his daughter when necessary? I think that it needs to come from him rather than you at this point.

Your BF needs to have a private talk with her pronto. BM has wind of her liking you and, trust me, BM is reacting.
Unless you have plans to take this girl on as a stepparent, get BF to tell her she is not to be rude and explain you are very happy not to be her mother, you have no interest or need to fill those shoes, you and he both have no problem with the kids mother and the kid needs to settle, Petal.
She will report back to BM who will hopefully settle herself down and if kid says "you are not my mother" again, the suggested reply would be:
"I'm so glad you understand that too because it's the last thing I want to be. You have a mother and I have no interest in that. However, you will treat me with more respect in the future because I am not nobody either. I am your fathers partner and an adult so let's agree to treat each other with more consideration - deal?"

SD went through this bratty period at about 12yo. Personally, I countered the "not my mother" with a wicked grin and evil laugh & told the stranger I was indeed the wicked stepmother. It usually defused the tension - not to mention to took the wind right out of SD's sails. I followed it up with a month of "I don't know, I'm not your mom, go ask a parent."

When in doubt, I assert myself by using pointed questions.

"You are not my mother." My response: "So what?" Or "What's your point?" It gets to the root of what she's saying and why.

Actually, that would be my response to anyone who tried to check me/shut me up ("...And your point is?"). Kids are no different.

I don't think it's respectable to wait for BF to stand up for you, nor to explain your role to a CHILD in the middle of a pissing match. Wait until the proper time and confront her about how you want to be treated/talked to. Be stern, but gentle. Kinda like how you would confront a woman at the office who got snippy with you during a staff meeting.

I'm learning that if you want to be respected by these kids, you have to earn it yourself. You're smarter than her. Remember that always. You're smarter than virtually every kid you encounter. Treat them like adults --- very dumb adults. OUTSMART her. She's seven. If she gets shitty with you, get shitty back...like a lady. A smart, sassy lady who can trounce a kid in every way possible. She's no match for you. And if she keeps acting up, it's HER loss that you're not her mother...because you would teach YOUR daughter how to be polite, a skill that would help her in every aspect of her adult life. Her loss. }:)

My dd has been in public with my mom and folks thought she was the mom, oh well, not their problem or concern, people think I am the babysitter of my older ss's and that's their problem I owe them nothing. When I am with my young sks and they are acting up, I am glad they call me by my first name! Let folks know I am NOT the mama or think I am the nanny, dont care! I am glad they know I am not the one who raised SD to help herself to things and throw the wrappings on the ground and cry when confronted. But my sks ALL know I am NOT the mama and that is MY house with their dad, therefor, we both make the rules and we both carry out the consequences. Don't want to clean your room? Cool! Sit there all day and come out only for meals! Want to be rude? Cool! This is a two parent home, one can stay home with rude one and one can go out with the better behaved kids. We are a team eventhough I am not the mom. When it comes to the discipline we are both very detached so to speak, there will be no yelling no emotional tantrum on our parts. You do what you are supposed to do before the fun happens, work then the reward or there will be no reward. I have no problem to watch all the polite kids play outside while one sits inside, I will bring all the computer mice with me, all the phones, and all the tv remotes with codes. }:)

This is one of those that honestly its probably better to allow the kids to respond. For kids its pretty simple, black and white stuff, you are not the mother and its perfectly ok for the child to say so if someone makes that error.
There is really no need for it to become awkward.
Sometimes my SD will say "Thats not my mummy thats SecondGeneration" and I fill in that im her dads girlfriend, othertimes SD wont say anything. She is young (stb4) so maybe as she gets older she will decide to answer back differently.
But the whole "you arent my mother/parent so I dont need to listen to you" I put that at the same teenage smart arse remark as "your not the boss of me" they just use the parent title because people get all offended.

I think that happens to almost every step. Strangers always assume the kid is yours because step-families are sooooo unusual (sarcasm). Give it time because after a while, SD will stop saying "She's not my mom." She will probably just ignore it eventually. As for her telling you "You're not my mother" I never say a word to my SD about chores or fighting with DH. I let him handle her 100% because it will always end bad if I get involved.

Re: strangers, how SD9 says "she's not my mom" matters to me. If it's got a friendly, informative tone, I don't mind it as much. But often SD had a defensive/rude tone that sounded to my ears like "UGH I'd never want HER to be my mom!" (me neither!) and, I think, sounded to the stranger's ears like "how rude of you for saying that!" Wasn't always strangers--this summer I picked her up from summer camp and I heard her saying that to other camp kids and counselors a few times before I finally addressed it with her dad.

Anyway, her dad explained to her that A. she needn't ALWAYS correct people (which she needs to work on in other aspects as well), B. it's nicer to introduce someone by what they ARE rather than what they are NOT ("Oh, she's my dad's girlfriend," which respects my place in the family and doesn't leave the stranger with no place to position me), and C. that she needs to take the edge out of her tone when she explains. I don't think we've much encountered this scenario since then, so I'm not sure if she took the lesson to heart, but I was much happier once her dad explained all that. Otherwise I was this close to making a shirt that said "NOT HER FKN MOM" and wearing that to the next camp pick-up (with "Dad's Upgrade" on the back, haha).

I am a proponent of the direct approach.

“Her dad is my boyfriend.” - Direct, factual and to the point.

“No I am not your mother (if you want to make more direct point you can add a “Thank God” here) but I am an adult, you are in my presence, and you will speak to me and treat me with respect or I will smack your butt (or stand you with your nose in the corner, etc…). Got it!!!” Direct, focused on the issue, and gives her call to action and outlines a consequence if she does not act accordingly. If she gets lippy, follow through.

Kids mirror the bullshit their parents feed them. This is pure BM BS no doubt.

BM telling her that you are not her mother is perfectly accurate but if one syllable follows “She is not your mother” other than “but she is an adult and you must treat her with respect” then BM needs a smack down. Rarely does a bio-parent give a kid clarity that they must respect their Step Parent in the other half of the blended family equation. “She is not your mother” more often than not is followed by something along the lines of “and you do not have to listen to her.”

Kids who are fed this toxic bullshit need clarity quick even if they are responding to toxic bullshit from mommy or daddy. The kid suffers the consequences of their toxic parent until both the kid and the toxic opposition parent correct their bullshit behavior.

IMHO of course.

It is easier when married- I just chime in "Stepmom" when someone calls me mom. But I think it is probably important as the adult in the situation, to say "I'm not mom, I'm Angelika." with a smile. Especially since sd seems sensitive to it.

I believe dad should do most of the redirection/correction but sometimes you'll have to. When you do- be clear and firm (but kind :)). When she says "You're not my mom," answer just like you said, "Nope. But I am an adult in charge of you at the moment."

Kids don't get away with "You aren't my mom" with teachers or anyone else.

Sd listens to me better than she does dh, because from the beginning I was firm, clear, consistent and she knows I say what I mean and mean what I say.