As I've said before, I'm not leagally obligated to give her any money at all, none. If you are infering that she's nothing more that a tax write off to me, I could put much more money in my pocket in the long run by cutting her off completely. You sound like a liberal in that any reference to making sure your own finances are secure is seen as greed.
Cut her off. Her entire future outlook on life may depend on your doing the right thing, the hard thing, whether you can claim her as a dependent or not. She clearly demonstrates that she has no desire to depend on you for anything other than money. This day had to come, it just came sooner than you expected. So, grant her the deepest wish of her heart: to be unaccountable to you. Will it cost you? Yeah. Is it fair? Hell no. But why let her own you and your peace of mind?