do i have the right to be mad at girlfriend for hanging with another dude?

Ok here we go. My girlfriend(sunshine) says she is going out with best friend who she aint talk to in a long while. They are so engrossed in catching up that she doesnt hear my phone call and only after seeing i called she text me back. It would be too rude to call me and say anything cause her friend aint having it so i chill and wait to hear from her the next day. The next day when i call she goes on to tell me about some dude who presses up on her the whole nite and just joined their little twosome and had a three way convo all nite. Now here it is her friend having no problem with her with a man she dont know all up in her face but she has a problem with her talking to me on phone for a minute. I got many issues with the whole thing. Should i just let it go?