I don't know what to feel. help!?!!!!!!!!!!?

Well I hae a best friend. We started hanging a lot like 2 years ago. She's a darling. she's really nice and trust worthy. I know i can trust her. <3 we're like always together and we're like partners in crime. ;D but, she's been hanging a lot with a friend of ours whom even she said wouldn't change when she obviously started talking about us. the girl said by bestie was a show off. like 5 or 4 months ago she mentioned that her mom was maybe gonna let her go to a concert she perfectly knows we both love the singer. I thought she was gonna ask me to come, she was kinda implying it. i found out like 2 weeks a go that she invited the mean girl. when i found out i started crying, so much that cried myself asleep. i asked her about it and she was like yeah im going :). and then i told her that i knew whom she was going with, and how she'd been ignoring me. (<------true) and how i felt depressed lately. she just said she felt really guilty and was sorry. (as im typing this im even teary eyed) i really don't know what to do. the mean girls even keeps bragging about. i don't know whether to go the high school that goes along with our middle school where all my friends and bestie will go. or to go another school where i can meet new people, and forget. i also don't wanna be there when they go to the concert. i just won't be able to hold myself from crying right then and there. I DONT KNOW WHAT TO DO! she's also been separating little bit from me. i feel like i was deeply destroyed inside. :'''''( I don't whether i should be happy, sad, or mad? please help me someone quick!