Is this backstabbing???

My ex boyfriend pretty much cheated on me with a friend that i've known since i was very young. Now i'm marred, but i still hold a small crug on this chick. Yesterday was my birthday, and i sat in my room all evening during my friends party with my baby while he was downstairs in the party. This morning my brother told me he saw my husband with this chick sitting next to her in a crowded couch, so very close, talking to her. Plus, my brother says she was very flirty. Is this betrayal that my husband talks to her after he knows how I feel about this girl?? Am I just bieng jelouse??? Should I forbid him from talking to her next time where in the same room as her??? Do I have something to be angry at. Becuase right now I am sooooo pissed off.