I think you have the right idea in letting her do her own thing, but also letting her know you are there for her should she need anything.

FWIW, I wish I had a sister like you I could have called on for guidance and support, I'm sorry she doesn't appreciate your willingness to provide that for her. I can tell from your post you are wishing to do so out of love for your sister and not a need to "one up" her or boss her about