I can understand why your a little mad. But your parents are right the baby cant go in the car and I can understand she would feel uncomfortable breast feeding in a strange place. I take it you dont have a child?
I think a lot of events that were out of your control all came together and now your feeling a little ket down by it. Try to forget it and move on? Hard I know, I think you might be mad at your other friends for not comming and are taking it out on the one with the baby, at least she turned up... Its hard being 21 I should know its not much easyer being 22 you just learn more on the way!
I hope you feel happyer soon!