I cannot say whether you should want to or not. I suppose the question is, if it's mainly just for sex, how will you feel about it after she leaves? Will you feel satisfied, content and happy that you did it, or guilty and bad about it? Maybe it's hard to know how you will feel unless you do it. There's nothing wrong with hooking up just for sex, intimacy and comfort, which is what I am guessing this woman needs and wants. It's a matter of how you are going to feel about it afterwards and how you're going to feel about yourself. You mentioned the word dirty. Will you feel dirty for doing this?