Cannot remove Family Sharing from my Daughter's phone

We have a big problem with Family sharing and the Apple ID on my Daughter's phone.

Before she had her own phone, she used my old ipad. Then recently she got a new phone, but she has my old apple ID on that phone now. My daughter is 12.

1. She has her own apple ID (we actually logged in on apple website etc), but I cannot replace mine with her own ID
2. Also, somehow she was the 'organiser' (using my adult apple ID) of Family sharing. We followed all the suggested step (First we removed me and my wife from the existing family sharing. Second we set up a new family sharing via my wife and invite my daughter. When she received the email notification and clicked 'joined' she got the notification " you are already in another family" with the advise to leave the current family first.

The only suggestion that I saw that I did not try ( but this is a bit of a nuclear option) is to ' restart phone and reset to factory settings'

What is the advise? Thanks!