toxic friendship?

my friend in sixth form is acting really weird. she has a boyfriend (who doesn't go to the same school), yet she is talking to so many other guys and has crushes on other guys. her bf does not know this and I personally find it bad because they have so many bad arguments on the phone, resulting in her crying at school, but she is basically cheating on him. but that is not my business.

I wouldn't say that it's a full on crush, but I do have slight feelings for this guy in my chem class. he is a real sweetheart to me and offers to get me things and though I am a really shy person, he tries to make conversations with me (this is a new school for me so he is a new classmate).

my friend seems to also have a massive crush on the guy I like, but I always have to pretend that I don't like him so that she won't get a bit 'angry'.
like whenever she sees him in the lunch queue, she tries to run up to the queue so she can stand next to him - they don't talk but yeah.
ever since this open evening where they were paired up to tour these families around school, she's been obsessed with him. ofc I couldn't care less as like I said, I'm happy that she got with her school crush. he hasn't talked to her after that day though. they have friendly smiles when they pass each other in the corridors but that's about it. no other communication since that open evening day. me and him really lacked communication, until today, because I get shy and I don't like to talk to people that I like first. I talked to him loads today and when I told my friend, she looked jealous. I don't get it. whenever stuff like this happens to her, I get so happy for her, but she just said 'aww' with a straight face and turned away. that hurt the most icl because she is a really close friend of mine