I don't know.
As one who has gone through divorce, I tend to take things like this more seriously than most.
There was a thread where the wife spent all her free time riding with groups of men and the husband asked if she could get some female friends to hang with and spend some time with him. There was another where a guy hid a $2k bike from his wife and she was beyond furious. "When is it OK to lie to your wife about how much things cost" threads come up from time to time.
People make jokes about these threads but some of them are indications of serious problems in people's marriage, or at a minimum, a disordered understanding of what marriage really is.
Maybe the OP's wife said it jokingly and I hope so. "I feel like your mistress" however, could be the the OP's wife trying to tell him something which to her, is serious. Only the OP and his wife know for sure but it might be time to book a long getaway weekend, something which is nowhere near a bicycle museum.
The jokes are funny and everyone has to live their own life but I hope train wrecks don't happen because people failed to see the signs.
-Tim-