I don't understand why it's a problem that I want my baby... my sister came home from school last…

I don't understand why it's a problem that I want my baby... my sister came home from school last night and met her for the first time and has had her ever since. I've only had her to feed her. I texted my mom to talk to her about how I'm upset about not holding my baby or being able to talk and play with her all day and she's being a bitch about it. Wtf it's my child