It sounds like her upset has nothing to do with the trip. It sounds like something else entirely might have caused her to be upset or moody and it just went downhill from there. Sometimes when you are finding yourself questioning where certain moods are comming from, as I said, it may be something else completely. We all displace frustration from time to time. I would say try and find out what was actually bothering her. It may have just been a bad mood that turned for the worse.