Am I just being jealous

My husband and I have been together for 21 years and marriaed for for 17 years. About 9 years ago, we had a really rough patch when he started having an emotional affair and I ended up having a physical affair (as retaliation in my mind at the time). He didnt see the signs that she was wanting a lot more until it was too late. She played the "needy" card and my husband being the kind heart that he is fell right into her hands. It started out slow and progressed to taking our kids to the movies with her and her son when I was out of town and always being there for her because she didnt have anyone. Anyway, we agreed that there would be no more single friends (she wasn't single when we all met) unless it was same sex friendship. My husband was introduced to a woman (she was a monetary sponser for racing) about 2 years ago, through a mutual friend. She was in a relationship so I never thought anything of it and there was only communication about money for racing anyway, but over the past year, her partner moved away and she is all alone with her teenage son. My husband sees her as a person that doesn't have true friends and he again thinks that he needs to take care of a helpless woman. They text off and on all day. She is always inviting him to things like to see her son march in a parade or at football games, knowing that I have to work, but I am always invited to come when I get off work and he goes thinking he is supporting the child, which would not bother me if this were his child. Now she does invite me, but it seems like an afterthought most times, and my husband gets upset if I ask him to wait to do things until I get off work. I am only trying to be logical in the sense that we would not have 2 vehicles where ever it would be. We have gone to various functions with other friends and they have even made the comment about how she looks at him and acts. I have tried to talk to my husband about this, and he just gets upset. I just wish he could see through my eyes what I see. Please help me figure a way to get my husband to listen without reacting. He has tried to get us to do things together, but it seems the only thing that we have in common is MY husband and I really have no desire to be her best friend.