C.V.
Invite her out to lunch or coffee and sit down and talk with her about all of this. She's an adult now. You needn't guess. Simply explain your concerns and ask her just what role you are to expect to have in her life, if any. Ask her to be honest and forthright, and do the same. There's no reason to circle around one another, nervously trying not to offend.
ETA: I think you should be the one to make that contact. Out of the two of you, you are the more mature and should take the mentor role. In order to relieve either of you feeling that you're being pushy about it, maybe just hold off until after the wedding. Send a lovely card and gift, but just let the whole situation be for now. Once she returns home after the wedding, call her and ask her out to lunch. At that point, all the stress of the wedding will be over, all the family drama will be through, and you can speak to her about your relationship without wedding weirdness muddying the water.