It really depends on the teen, OP. My teens are not party types, and they won't destroy your stuff, but they might forget something, especially in an unfamiliar house - maybe forget to lock the door at night, or lock themselves out, or leave lights on when they shouldn't, things like that. So if you think this girl is serious and responsible, help her out anyway by making a highly visible checklist she can consult. And if you have code-entry door, she doesn't need to remember to bring the key. You might also allow her to invite a quiet friend over, because two weeks will get lonely, even if she can go out and meet her family and friends.