This actually happened to my husband. I feel that I would be concerned for her well being if he seemed to be at all shady and concerned for him if she was to act strange. If both are adults and happy, then I wouldn't be upset or judgemental. My opinion is that age should not dictate whether or not people should be allowed to have a healthy, happy relationship unless one of the parties is either underaged or of a vulnerable older age.

As for my husband's situation, his mother has a screw loose and was having an affair with a married younger man who was jobless and a druggie. Though he detests both for their issues, his dislike has nothing to do with their age differences. She started her affair simply because she wanted to relive her teenage years. He went for her because she supplied him with cash and toys. The victim in their situation is his two year old and his four year old daughters and his wife. They eventually married after my husband's mom footed the bill for a great divorce attorney.

If my father pursued a younger woman, I think I would have a slight problem with it, simply because he is not a very healthy guy and I'd question why a woman would want to chase my father when he has heart problems and doesn't really find younger gals all that interesting. But mainly that goes with the "vulnerable older age" bit I mentioned earlier.