What state are we talking about?
First off, a domestic partnership is not just "living together" in most states that recognize it. It's tantamount to being married and has to be dissolved through a court process. True, domestic partnership doesn't count for getting a green card any more than living together, but the fact that she has a very strong tie to you is a basis to assume she might have immigrant intent on a subsequent visa (the fact that she keeps stringing together multiple non-immigrant visas isn't helping).

