My girlfriend and I had plans to go to San Jose this weekend to see her friend. But then she tells me her friend's boyfriend is not going to be there so she would like to just hang out with her friend, have girl time. It's a little annoying, yeah, but I accept it. We make plans to go see a movie when she comes back on Sunday. Then it's Sunday and I'm waiting for her to come back but then get a call and she says she's going to stay another day. This really annoys me. I hate the feeling that she's not making an effort to see me. But then I think, should I also just be understanding that she wants to spend more time with her friend she does not get to see so often. It's a weird place to be.

Why not take this chance to spend time with your friends?

Go do something, you will have plenty to talk about when she gets back.

Freedom within the relationship is important for both of you.

Space can be a good thing. You seem to be worrying a lot when you seemed to have answered your own question. It is healthy to have a balance between friends, family, and your lover. If she wants to spend some time with her friend that is perfectly OK, you can use this time to do your own thing. You are an indivual, your relationship shouldn't define you, just maybe complete you. If she's with friends, you can be too. This is why it's good to maintain a good relationship with friends when you start dating. If you ditch them all, you have no one to go to when your other half isn't there. Hopefully this isn't the case for you.

Good luck.

Yes you're wrong.
How long have you two been going out?
If you've just started dating, and you are This controlling, I'm sure you'll find her making a Great effort to Not see you!
If you've dated each other for a long time (I doubt this), then you probably must learn to give her some space.
I spend A Lot of time with my group, best girl friends only. If my boyfriend ever complains about it, he's in big trouble. Being in a relationship isn't having full control over the other person's space and time. I'm also busy with my job and university, he is too, so we respect and don't ever invade each other's privacy. If my boyfriend get all needy and following me around like a lost puppy, I wouldn't be hesitate to shoo him away. It's a Big turn off for girls if their guys don't have anything better to do than talking to her, missing her, etc. You get what I mean right?