Dating: I feel like I'm not a priority in my girlfriend's life

My girlfriend and I have been together for a year and a bit and things are generally going really well. We’re both in our early twenties and just out of school. When we’re spending time alone together, I feel like I could easily spend the rest of my life with her. The problem is that our relationship doesn’t seem to be a big priority for her. I know that she loves me but it’s seems like to her having a boyfriend isn’t as important as other parts of her life. I’m sure this is because this is her first relationship and she’s always been quite independent. That being said, she’s also a very social person and her friends and family are very important to her. She’s a people pleaser and doesn’t want to let anyone down so she ends up having more things to do than she has time for. So, it usually ends up being our time together that gets cut short. I’ve talked to her about it and we’ve sorted out some communication issues which has helped. Anyways, getting to the point, the part that’s still frustrating for me is that while she doesn’t cancel last minute as much anymore, my girlfriend doesn’t try to make much time for us in the first place. At least not as much as I think we should have together after dating for over a year. She does initiate plans but mostly when there's something specific, she wants to do and asks me to go with her. Maybe I’m just being too needy because it’s my first relationship too. She’s working 6 hours away during the summer and she doesn’t get a ton of time off and since it’s sporadic it’s difficult to plan anything in advance. But I know there’s not a lot that can be done about it. The one thing we did have planned was to go to California or somewhere else for a week with just us, between when she finishes her summer job and starts teachers’ college. But a couple of days ago she told me that now she’s decided to lead a canoe trip at the camp she used to work at instead of going with me before she goes back to school. She could tell that I wasn’t terribly happy about this and said she felt bad and that she knows she always cancels things. She said that she felt like the people at the camp were like family to her and she missed them and that she felt she had to help them since they didn’t have enough staff. This is understandable but it makes me feel kind of useless. Doesn’t she miss me too? I’m pretty certain her coworkers wouldn’t be there for her if she needed it like I would be. She tried to tell me that we would still have some time together this summer but it’s really only going to be every other weekend at the most, and likely only once or twice a month while she’s at school. Most of this time we probably won’t have alone since she lives at home (45 minutes from me) and doesn’t have her own car. I know she’s really busy so it isn’t possible to see her that much but if I were in the same situation, I know I’d be doing anything I could to fit in time with her. Don’t get me wrong, I’m not being clingy or anything. I still have my own interests. I just try to plan them so they don’t cut into our time together. Am I being unreasonable? If not, how should I explain this to her? It seems like when I try to, she thinks things are fine and that we’re spending enough time together or feels that I’m trying to push her friends away (she told me once that her friends said she was spending too much time with me – the ones who don’t have boyfriends, most of the ones with boyfriends have already moved in together). I was hoping that now that she’s finishing university, I’d be a bit more of a priority but I’m worried that this is just the way she is and expecting her to make more time for me will just leave me disappointed. I don’t want to lose her but things aren’t working for me the way they are. Any help to resolve this would be very much appreciated.