Best friend advice?

So my best friend of almost 10 years has been acting strange lately. We’ve never fought, but as soon as our senior year started she began hanging around other people. Its really odd to me because I just thought about becoming friends with these new people but she told me they don’t speak any english and that they don’t like white people. This actually ended up being true, they really didn’t want to talk to me because I am white. The situation totally threw me off because if they are prejudiced against people like me, then why would she hang out with them?

Furthermore, she’s always been really adamant about going to college and becoming a nurse her entire life, but now all of a sudden she meets this 25 year old guy and throws all of that out the window. She didn’t even want to tell me about the guy either, I found out from someone else. Not to mention, she had a really bad history with an older guy she dated before being controlling, so I feel like she should be a bit smarter when it comes to dating guys.

I don’t know what to do because I don’t want to lose our long friendship by confronting her, but I also don’t want to be excluded, lied to, or kept secrets from. I understand people change, but it’s literally been two months since our last year of school started. I find the whole situation just confusing and weird, any advice would be greatly appreciated.