Do you really need people on the internet to tell you this man? There is one of 2 possibilities here... Either she is lying to you and just wants to continue banging him while using you, or she is legit being threatened about it at work. If that's the case I'd find it difficult to even give a shit as she cheated on you in the first place. She made her bed, let her lay in it. She needs to report him and/or find a new job. Either of which is not your problem. You're 22 man.. Youve got plenty of time to find someone actually worth your time and effort. End the relationship and walk away. She chose to cheat. Let her figure out the problem she created herself all by herself. If you stay with this girl even for another day you are a complete fool and whatever she does to destroy you further is on you.

Know your worth man.