Are they my friends??

Hello all, I’m looking for advice or a second opinion on an issue. I’m in college and my school is very small so it’s a little harder to make friends. I met a girl who I clicked with really well and we would hangout all the time. She one day introduced me to one of her friends from high school. Her and I clicked well too and soon enough we were all good friends but I slowly started to notice that my friend started to drift a little and then noticed that they only ever hung out with me when we partied or were drunk, but they always did other bonding things without me. Even when I would say I wanted to be apart of plans they would “forget” that I said I wanted to come. It finally got to me and I told them that I understand that they had a stronger bond and that we didn’t have to do everything together but that I felt like I was getting left out of everything and wanted to know why. My friend said she didn’t realize it and that she was sorry but the second friend said that it was stupid that I felt that way. I’m already cutting her off because I feel if you tell someone how you feel and they say it’s stupid then that’s a red flag. But my other friend seemed to try to make it better. Im wondering if I should put it behind us and just be friends with her or should I let her go too?