My husband has a friend at work. 5 years younger, very slim(compared to me) pretty. She is married with children, as are we. They have got close since starting a new job at the same time. They spend lunchtime together and are, in his words, best mates in work. She invited us over to her house at the weekend and we went with children.. she was nice, if a bit different to us (more outgoing and quite loud). There was no indication of anything going on and her husband seemed comfortable with the friendship. But I can't shake the feeling that something is not right. They spent lunchtime together yesterday and it made me unreasonably angry and upset. But I have no reason to be. What would you do and what would you think?