Songs and ADVICE about friends kind of ditching you?

my best friend (girl) comes over before and after summer school-im her carpool-shes my best friend in the world and im hers. our other best friend is a guy (they were dating but then broke up, now thye are kind of friends with benefits) and she hung out with him 3 days ago. i havent hung out with him for a week and a half because i was on vacation. so today i left school early to go to a picnic for my dads work. she went to another friends house after school and when i got home i texted her to see if she was going to hang out with our guy best friend today. she said no because she had to go home in 10 minutes. i said ok well if u do let me know so i can come with. 2 hours later i was walking with my cousin and i see her with the guy and 2 other girls and another guy. they all ran over to me but i walked away. she keeps saying shes sorry and she wanted me there yet she didnt invite me..? im really mad and confused on why she would do that. i dont know what to do and shes coming to my house tomorrow morning. what do i say? do i even talk to her? what are some songs about this? thanks sooo much you dont even understand how much this means to me.