Daughter’s new iphone

I just purchased a new iPhone 8 for my daughter. I have sprint and bought through their website. When the phone arrived, I tried to set it up using my Apple ID since she’s 12 and doesn’t have an email. This seems to have connected her phone to my iPhone. I set up family sharing from her phone. I guess I should have set it up through mine. I don’t know how to fix this. I don’t want our devices to be connected. I want her to have her own account but I need access and parental control. Can anyone please tell me how I can fix this?