Hmm.

I don't think that your wife *needs* to know that you find younger women attractive. If she considers the woman that made the pass a good friend, it might be appropriate to give her a heads up that the woman made a pass at you.

Why do you hesitate to tell her? What outcome are you looking for by telling her?

I sort of assume that my boyfriend finds attractive women attractive. I don't really want him to tell me that, though. If you want to talk to someone about these feelings, I would go for a same-gender friend before discussing it with your wife.