How could she do this to me

She is entitled to other friends. Although why not ask her about your trip together and start arranging that

I've been mates with my best friend Heather for 10 years, and we've always been close. We're both going to seperate unis in September, and we promised each other that we'd do something really cool and go away in the summer. Now I've only just found out that she's planning a trip with her other other two mates for the summer and she hasn't invited me. They now spend all their time organising their trip and what stuff they're going to do. I said how excited I was for her but I can't help but feel hurt. I feel like crying because she has left me behind when I was supposed to be her best friend. I've got other friends I'll be spending time with, but I've always included her and she knows how much I love going on trips away. I don't want to say anything to her, but it makes me feel upset to think she has forgotten me. Is she being selfish?

I think she's probabaly just not realised that this is quite insensitive. Maybe she thinks you wouldn't want to go with these other people?

Why are you telling us? You should clearly be talking to her about it.

Does this trip with her other friends mean that your trip is cancelled?

If no, then I don't see what the problem is, really. If it does, then have a word with her about plans for the summer, where the two of you were planning to go, see how she reacts...