My girlfriend says she misses me but has control over when she can see me?

Hi, thanks for visiting my question.

I am 15, Male, and I have a girlfriend who is 16. We are both virgins although we've been very physical and close to sex we just haven't had the right time or place to do it yet.

My girlfriend lives 30 Miles from me and has fairly strict parents, she can only come out with me on weekends. She is part of a youth organisation that gives her optional choices to go and do courses on certain subjects. These are very useless and unrecognized by society as she has told me.

However, she is always choosing to do these courses a lot, and this means that we spend a lot of time apart. Which causes arguments ect.

She'll always text me saying how much she misses me and that she wishes she was with me, but I'm really not understanding why she's always choosing time away if I'm so special to her and she needs me so much?

I don't really feel like just asking her to not go on them because that just seems selfish and shallow, but I really miss my girlfriend and she seems to be missing me, so I don't understand why she doesn't just prioritize me instead?

Thanks in advance