Having a hard time with my 13 yr old sister rn

I’m 24 years old and I’ve recently gotten custody of my 13 year old sister. She has a history of extreme early childhood abuse that happened when she was like 1-6ish. And recently she had an attempt and she’s currently in impatient care. But when she found out that when she comes home she’ll have to be in day treatment for the summer she said she’d rather stay impatient or go to foster care. I feel like she just overwhelmed and wants to go home, though I’m not sure if that’s really how she feels indefinitely. Any advice or help would be appreciated. I’ve struggled with my mental health as well but not to this degree, this is the first time both me and my sister are working with this kind of care.