Keep it your secret, Jim...
No need to risk a good friendship..

Once you tell her she may feel awkward in your company, knowing you fancied her so long ago and her husband may also get to hear and he too would feel perhaps different towards you...

And that's not to mention how your wife might feel....

It's in the past and you get to share her as a good friend.

Let Sleeping Infatuations Sleep.....