young adult stepkid is now shunning me

horribly long post sorry in advance. the title sums it up. my stepdaughter has been quietly competing with me (and also often competing both with and for the attention of her way younger half-sister) for attention from her father, while sending me the message that i am NOT HER MOM for the last decade. mostly passive aggressively by trying to hold long exclusive conversations with him while basically pretending i am not there for like 10 whole long years. meanwhile i helped raise her regardless, 50% of the time, made sure she had food on the table, and excused myself for a lot of long walks and solo activities so she could have her dad to herself.

finally college came.

the older stepkids had taken over the little studio with its own bathroom and kitchenette that we have, as their bedroom. this is our financial situation, that was the room we had available for the older kids, as their halfsister (my biokid) needed to be in the 2 bd house closer to us due to being a toddler and little kid.

the oldest kids fought with each other a lot over wanting the studio to themselves and had territory battles. i told them both once they were in college i was going to rent it for extra money, that we need. the eldest never had much competition with me and we got along pretty well, but after they had already moved out the middle child who competes with me constantly reallllllly took over the studio and basically trashed it with knick knacks. after months of years of verbally warning that the space is SHARED and would be tidied up to rent, she went to college and left the place buried in mountains of doodads.

as afore warned i went in and cleaned. fast forward winter break she flipped out and had a temper tantrum and now refuses to stay with us in the guest house (100% available to her, as well as others who need it).

she is now passive aggressively refusing to communicate on any family text threads that include me. she will only communicate with her father. he’s asked her to include me and she ignores it so it’s very deliberate. he says she’s mad i touched her things. but the worst part is that she’s sticking him in the middle of this weird made up passive aggressive communication battle, and he just seems so DEPRESSED about it. i feel really awful for him. i have no idea what to do in this situation. i’ve never had any power with this kid and i sure can’t help her behavior now. it’s almost like now she’s in college she’s feeling empowered to really lean into the rejection of me she’s been harboring this whole time. in a way i feel like she’s entitled to that—you don’t have to accept a stepparent if you really don’t like them or want them around. but it’s kind of a messed up for her dad and her half sister. hurts my feelings too, but mostly i could just do without her negative energy constantly directed at me. no idea how to handle this situation gracefully.