Am i in the wrong here?

Hopefully this is okay in this group. Due to some unexpected news that came up, my *foster* daughter is now being placed back with her biological mother. She is 16 now and I got her when she was 11. We never expected this to happen but unfortunately there is nothing we can do (for now). We were not able to adopt her. We wanted to but were denied because of the birth family situation. Before I go on about the issue, I’ll just make it clear that I am ALL for keeping kids with their bio parents. I think it’s so important to keep that relationship. But she is MY baby. Im her mama and she needs me. My daughter fully plans to move back in with me in 14 months once she turns 18. The current issue is this. I have bought my daughter so many things over the years. She has an iphone, a MacBook, a camera, tons of designer clothing and makeup and literally all of her belongings. Her birth mother refuses to let her keep them. She says she doesn’t want her owning any of these things. She even stopped letting her go to her dance classes which she loves more then anything. And her tutoring. I told her I would continue to pay for her phone if she could keep it and i would continue to pay her dance lessons and tutoring. I asked if I could give my daughter a $500 monthly allowance for her wants/needs and she is denying EVERYTHING. Im completely disgusted and heartbroken for my baby girl. She’s 16, almost 17 and this has been her life. I don’t think it’s fair at all that she is having everything ripped from under her. My daughter has begged her and begged her to see me and she wont let her. It has been 2 weeks and my daughter has already ran away from her bio mothers home twice and came to my house. The last time she was here was yesterday and I gave her money and told her to keep it for herself and not let her bio mom know (i know I shouldn’t be asking her to keep secrets but she’s old enough to understand). She hates her birth mother (her words). The birth mother has told me to stay out of hers and “her” daughters life and that i have no business with them anymore. Im obviously not going to stop fighting for my daughter and her rights but the birth mom is telling me I’m out of line. She wasn’t a good mother in the past. She doesn’t care what she wants or needs clearly. I know my baby will be back with me soon but I don’t know what to do until then. My daughter isn’t allowed to go out or do anything. She’s been allowed to have 1 friend over once and she used her friends phone to secretly call me and all she did was cry for 3 hours. My daughter has the most beautiful room here and everything she could ever want and need. Her room at her birth mothers house is a single bed with DORA SHEETS, dora curtains and a desk with no chair. That is all she owns. She has 4 outfits which she hates and wasn’t allowed to pick out. I could go on forever. What do you think? Am i in the wrong by being so persistent and “overstepping”?