Hm-m-m-m... well... I don't know as I really have an answer for this. (Perhaps the best solution might be to ask her what it's about?) Off the top of my head, I'd think perhaps it's anxiety. She likes the idea of traveling. But as soon as she's away from home, she gets nervous & want to go back. Perhaps she is struggling with some agoraphobic type tendencies. They may not be so serious that she can't be out-&-about where she lives. But once she gets away from familiar places, such as on a trip, she becomes fearful & wants to go right home. At least these are my thoughts with regard to your post.