Some people are born with a predisposition to mental illness, which is why it tends to run in family histories. I once dated a girl with a family history of schizophrenia, and the stress that brought it out for her was when she moved away to college. Consider this: some other people are born with a predisposition to alcoholism, though it doesn't mean the person will be an alcoholic (they may never have a drink), but once they have some drinks and become alcoholics, they can never be "completely cured" but are always "recovering." Same thing with mental illness: once people cross the line, it is always a struggle for them to cope with anxiety without slipping away from rational thought. And childhood trauma is the worst kind of stressor because the strong emotions are burned into memory, (and get reactivated with stress), and the fact that she suffered abuse from her family means that certain types of "family activities" (like holidays, graduations, etc) will reawaken her feelings of dread. The poor girl is damaged goods, so like I wrote earlier, you will need the patience of a saint to make this work. I feel like Sean Connery in Highlander when he says "I would spare you the agony. You should leave her, brother."