you can care about someone, and help them, and still realize that being in a relationship with them is damaging to you as a person.
i mean you're basically saying right now that you'd rather sleep outside in the balls-ass cold than bother to go home because you're afraid she'll get violent and you don't want to deal with that potential level of confrontation. that to me doesn't really sound like a good relationship, sounds like my parents, actually.
edit: actually now that I think about it i've slept in a car as a kid a few times because of shit like this. it sucked and was terrible. why would you let this happen to you as an adult?