Is this jealousy or something else?

My best friend(a girl) are supposed to hangout tonight at my town's annual Carnival. Also, she has a girl best friend, so I am basically her guy best friend. She isn't quite sure if she is going tonight or tomorrow though, but either way, she said we can hangout. I don't mind hanging out with her other best friend cause her other best friend is a really really close friend of mine also. But, these guys from her YMCA, that her and her best friend went with to Hershey yesterday because it was a YMCA field trip, asked if she found a time yet him, his friend, my best friend, and her other best friend, could meet up tonight to hangout at the Carnival. That kinda irritates me for two reasons. One, she said we could hangout and didn't mention these guys at all. And two, it is hard and awkward talking to her in front of other people she is with for me and I have no clue why. I don't know how to explain it, but how can I fix it? And is it that I am jealous, even though I don't feel jealous?