She spends more time away then together.. is our relationship worth trying for?

my gf Katie and I started dating in dec 2009, she is very active in a million different school functions, dance, volunteering etc. I love her and she is amazing.from January until mid Feb she went away to England for a school thing came home then in April she got picked to go out of town to help with the habitat for humanity and was gone for 8 weeks. I'm proud of all the hard work she does and how sweet and caring she is but its hard ebing away from her so much. She has only been home for 2 weeks and today she told me that her parent are taking her on a month long vacation to Europe in August. I want to be excited for but I'm not. I feel like our relationship doesnt matter to her but at the same time I know that she loves me if that makes sense at all. The last few times we have been together we ended up fighting because I am upset that she is aways gone. A part of me wants to tell her I'm done but I love her to much to say that. How can get my head to argee with my heart and make her happy