I know it's crazy, but hear me out:
Have you ever thought about… legally adopting your little one?
Some countries, don't know if everyone, but some countries, mine, for instance, allows grown ups being adopted by another grown ups (usually older people -- like, if the person being adopted is 18 years old and the person who is adopting them is 40 years old).
I known that this going full Daddy's Little Girl Relationship, but I get hard as hell just by imagining that….
You becoming her daddy, and, like, you having a DOCUMENT, an official document showing that you're her daddy.