My best friend is becoming self obsessed and different

So my best friend Grace has started to change and I don’t know how long I can wait. She recently had a boyfriend back in June but they broke up but I noticed some changes during and after.

For some back story she had always been decently innocent other than getting tied into sending nudes. Other than that she wants to be a traveling nurse and has huge goals and good grades.

So when she first got her boyfriend she started dressing more western, started going to parties, vaping, and drinking. It was super strange to watch her do it considering it wasn’t like her. Then she got into a new friend group on top of that.

But anyways after she ended things with her boyfriend she was fine considering they never even hung out alone together and never even kissed. So it was like a middle school relationship pretty much.

But anyways she started talking to three guys right after and now she is talking to even more. All she ever talks about is her boy situations. She hangs out with this one group of guys of which one of those guys I dated for five months. But she flirts with all of them even though one is a whole ass adult, she gets ab pictures. She also vapes with them. A part that annoys me is that in the past she flirted with every guy i have ever talked to. And my first boyfriend of which she convinced me to dump him, she ended up sending nudes to. And bow every time me and Grace hangout she invites someone with a vape to let her use in my car. She cant even hangout with just me anymore. She always invites someone else or is on her phone. I simply want an apology from her. I have never gotten one. She has done so much shit to me and has made me turn against my other friends and i am left with nobody but her. She doesnt even consider me her best friend anymore. She only hangs out with older girls and just uses me to fall back in when she gets lonely or wants to complain. I dont know what to do.😀