I'm sorry you're feeling so frustrated!

I guess my feelings on the matter is that she probably asked to stay with you because she thought it would be fun to hang out with you and stay with a friend. But it also sounds like this was a business trip, so she genuinely might not have time and will be tired at the end of the day, but if she had stayed with you, then she wouldn't have had to worry about making time. She would have been able to just unwind and hang out with you at the end of the day, whereas if she's staying some where else she has to make plans to go out and can't just go "home" and crash.