seriously, she gets to leave and have fun but you get to be the manager and take care of the road expenses and speaking to the hotel manager for her?
Whoa!
Boundaries.
Let her put on her big girl panties I believe is the term thrown around here. She's an adult, she can take of the logistics of the trip. She's having fun and that's ok but having fun without you but expecting you to take care of the details to enable her fun while you're not there... totally not cool.
Totally subservient behavior on your part.
You are the butler, you aren't the accountant, you are the personal assistant... stop acting like one.
Do you have a life, she apparently does, so why are you waiting on every text that comes from her?
No excuses.
Any excuses you have won't work.
Excuses don't explain and explanations don't excuse.