Yes she is attracted to him and yes she likes him. Odds are good that she has
cheated on you. A good sign to look out for in future relationships (not with her) is if all of a sudden her behavior changes for no reason what so ever. That's when you need to start asking questions and get to the bottom of it. When you do ask questions don't accept "I don't know" as an answer or stop asking if she starts to get angry with you.
Relationships are supposed to be two people wanting to spend time with one another. If they don't want to spend that much time together it's just a friendship. If she stops inviting you places then you should call it quits because the relationship is on it's way out the door.
If you get worried about one of
her male friends odds are something is up. Frequent calls, being a little too friendly is cause for concern.
Always question whether or not it's your paranoia or something is really going on. If she always includes you in outings, is honest and loving towards you it's probably your paranoia. If it's not then you need to address the issue.
Just make sure that she is leaking sexual energy from the relationship before you confront her. If you aren't sure you will get killed. A lot (not all) women are good at turning things around to make you doubt yourself. If you are certain that her behavior is unacceptable then you won't fall for the argumentative tricks.
The only way I would think of getting back together with a girl like this is if she was genuinely sorry for what she did and cut all ties with this guy. People do change but need to change their behaviors they are apologizing for or you will hear "sorry" a whole lot.