Welcome to PC waggonwheel33. I'm older than you so I don't follow the belief of hanging out with guy friends when in a committed relationship. I don't find you overly jealous and you said you were working on it. I do agree with you, it wasn't right for her to communicate with a guy at work who made it clear he wanted more than a friendship. The fact she went with him, right after breaking it off with you means she/he had those intentions. I understand who you're hurt and doubtful now.
Do you hang out with your female friends and is she fine with that?? Why can't you all hang out together. Not sure how to solve this problem because I can understand how you feel.