So should i tell my friend shes being a slut?

okay so i have been friends with my bestfriend for 11 yrs and just this summer ive only seen her mayb three times bc shes been hangin out with her cousin, and her cousin is kinda on tha slutty side and my friend has always been on the more well kept side but jus this summer alone shes dated i think five diff guys and dressin rly trashy.So i go over to her house tha other day and she is totally tlkin bout her cousin and now shes with her again,I dnt know what to do i dnt know if she thinks its bc im a virgin and her cousin isnt or she can get a guy and i cant, but i have been there for her when this girl hasnt and when rumors or girls were messin wit her this year i would take care of it and in return she treats me like crap like we were suppose to go see like three movies together and each time she has made up an exuse not to go and then i txt her and ask wht shes doin and she always says tht shes at the movies with her cousin seeing tha movie tht we were suppose to go see. Im asking for ur help bc i need ur opinion on wht i should do bc if i confornt her about it her it might cause drama and her mom has already threatin to send her to a diff school and i dnt want tht but if i dnt im scared tht shes gonna keep treating me tha same way!!