I think its okay to be honest. You had pure intentions, you wanted to help out your friend an offer her some respite by the sound of it. But in the end it might only make things more stressful for your friend if on top of whatever is going on for her she then fins herself facing less than happy insiders who are stressed out by having her there.
Can you offer her some fun evening time together (or whatever it is she needs) but explain that the situation is best if she doesn't stay after all? (With as much explanation as you feel comfortable with)