Don't stop her from furthering her education. Maybe you could encourage her to go somewhere in the US so you two could see each other more easily, but don't stop her from continuing in school. She will resent you for it later on.
As far as these other vacations, have you tried to make plans go to on trips with her? Sometimes girls want to go on trips with their girlfriends, and you should encourage that. However, instead of getting upset that she is going without you, try to make plans for a trip that the two of you can go on together.
R