Chrissy - that's a terrible accusation to make. I was unjustly accused of theft three times in my life and it still makes me so angry and upset to think about it. I would have a hard time being around that woman again. I might check in privately with the woman who initially invited you to let her know what's up, see if perhaps this kind of thing is normal and let her know why you might not want to do the sleepover thing.
"Any idiot can face a crisis; it is this day-to-day living that wears you out." -Anton Chekhov