I think my bestfriend is using me. But Im not sure what to do! Please read below and help me?

[Sian]

Well Ive been best friends with this girl (Im not going to name names) for about 10 years now, but ever since she started at a new high school shes changed SO much. She made new friends with a group of b*tchy girls and suddenly shes completely caked up with makeup, shes so judgemental towards others, shes become really self obesessed (like she actually says to me how she thinks shes so pretty) and flirts with every guy she sees. So lately shes pissed me off so many times, like when I told her who the guy I liked was and that he liked me aswell and she went ahead and added him on facebook and started calling him sexy "as a joke". A few days later I find out that he started liking her. And she also takes really horrible photos that I dont like if me and posts them on facebook without my permission and refuses to delete them. Im so sick of her just walkibg all over me!
Anyways, I found out that she was a bitch to the girls in her group at school and that she basically had no friends and everyone was calling a her a mean slut... So after months of ignoring me she comes along and dtarts wanting to hang out with me again all of a sudden! And then when her school friends come back to her she starts ignoring me again.
Ive tried talking to her and she keeps saying sorry but after a few weeks she always goes back to normal again.
So I was just wondering, should I end the friendship after 10 ysrs of being best friends or just put up with it for a little while more?

Sorry I made you read all that haha,and thanks xx

[Nadya]

Everybody changes so dont be suprised that shes turned into a ***** theres always one. just drop her. maybe if she has no friends she will become a better person