overreacting???

Shay
So over this past weekend me and my mom went to visit family and friends for St. Paddy's day. We went out drinking with a very close family friend who I hook up with once in a while. I felt sick and left the bar early, well my mom ended up spending the night with him. She gets extremely flirty with him and It's not the first time it's happened and I get very upset about it, they both know how I feel about it but continue to do it. They say nothing happened, but I'm still mad about it. Am I overreacting???