You do what is best for you. That is the first step. If that is best for you than do it. If not then find away to have some very clear boundaries with her. For example, if you are using you cannot stay at my place may be a good start.
I know this is hard but it gets easier. Setting boundaries doesnt mean you have to be cold or uncaring. It can be as simple as not answering the door if you know she is just looking for a place to crash. Or not returning a call if she calls under the influence.
It is about letting her know what you will not tolerate. But it doesnt have to come from a place of anger or rejection.