I would be honest with your wife about how you feel and how much her cheating hurt. Even if she is polyamorous, she didn't discuss things with you beforehand, and she lied to you about her attraction to her co-worker. Even polyam people can cheat. Her being polyam doesn't make it okay to go behind your back.
Healthy relationships, of all types, involve open communication and honesty, between all partners. Your wife didn't honor that, or her commitment to you. Of course you're feeling hurt and threatened.
If she wanted to get her needs met in a healthy way, she would have talked to you beforehand. You have a right to be upset, and IMO, she should feel guilty about what she did. If anyone was manipulative in this situation, it's her.