I would not engage them with that type of question, because if they're rude they could easily reply, "My wife/sister/etc. Wouldn't be silly enough to be out here in traffic on a bike" or some other idiotic statement, and you can see where that would lead.

I had some big SUV driving person in a big hurry honk at me yesterday when I was in the cross walk, simply because they thought I was going too slowly.