I need help! I need to know if I am being ridiculous for worrying about this or if I have any real concerns...

I know that I am a jealous person by nature... I love my husband, and don't like him getting close with other women. He does have a few female friends from before we became married (about one year ago) and I am fine with them, because he includes me now in their relationship... I am worried about a present situation though.

My husband has a female friend who is single and 8 years younger than him. He texts her and sees her often at work. Lately they have been hanging out just the two of them, and when I told my husband that it bothered me, he was upset. He said that he saw her as a friend, and nothing more, and that I was being ridiculous for worrying about something like that. I asked him to only see her on a professional level, and stop hanging out with her outside of work, and he became very upset. He couldn't believe that I would try to tell him who to hang out with.

Needless to say, he won the argument because he made me feel untrusting and controlling about his relationship with this girl. I try not to let them hanging out bother me, but it does. I also feel like he's acting differently lately... more distant with me... he says that's all in my head, and that I'm being silly. I feel like that if this relationship continues, that sooner or later it will not be just a "friendly" get-together. Am I crazy for thinking that this girl is going to fall for my husband? My husband said that if he noticed her acting in a "more than friend" way he would re-evaluate the friendship at that time, but honestly, unless she threw herself on him, I don't think he would be able to tell the difference.

Please help-am I overreacting and just being a selfish wife?