What Would You Do?

I need some input on my situation. I have been working at my new job for about a year and a half and I met this girl there who is really cool. I am the type to not really click with other females because they are real catty but this girl is so cool. I have told her things about me that I have never told anybody else. She is just a real and genuine person. So I went over her house for the 1st time because she invited me to her birthday party and her whole family was there. Craziest shit ever, her baby’s dad is my side nigga. She introduced us and I didn’t know what to do. He just shook my hand and said nice to meet you, so I smiled and said it back.

I am so confused, I don’t know what to do. She has been nothing but a friend to me and dude also has done nothing but play his position with me. Great sex, he helps me out financially and we have great conversation. I always knew that he had a girl but I never asked any questions about her. I don’t know if I should tell her that I have been dealing with him, stop talking to him, keep talking to him, IDK! What would you guys do if you were in this situation?