Hey man, thank you for sharing all of this with us! It sounds like you've found a girl with more to offer than just her hair and that is a good foundation for any relationship.
I saw good advice on your last post about how to proceed with her,but given that she already has ankle-length hair (a very rare length in the world) I would also recommend offering to help her brush/detangle her hair as your relationship gets more serious.
This will not only get her used to you touching her hair, but will also show her your love of her hair goes beyond just enjoying it superficially. As a result, it will be less awkward once you finally introduce your fetish to her.
Best of luck! I hope you have a bright future ahead with her!