Not sure on this one if IABU but this is really bugging me.
Dd is almost 7. Her dad's been with his fiancé for around 4 years (they had been together when younger too so has known her for years!) When dd is there she is involved in her care which I am fine with. She's generally a really nice person and dd likes her. They have a little boy together (6months) who dd adores aswell.
She (step mum) refers to dd as 'her' daughter and it really, really annoys me
.
I have spoken to dd's dad about and he did speak to her. There are comments on Facebook 'so proud of my daughter for passing her ballet exam' etc. Also a really gushy post on Father's Day about their family and their 2 kids.
She had requested dd spend another afternoon round there in the week (dd's dad will be at work so it would just be her and the kids). We don't have any formal custody arrangement as never needed it but I don't really want dd there without her dad one extra afternoon a week when I could have her at home with me.
AIBU? I mentioned it to a friend who says it's fine but I don't agree. 
(Dd doesn't call her mum, she has always just used her first name thank goodness )
AIBU? (If so, how do I handle it as I'm struggling with it now. If I'm not, how how do I fix it?)