I gather you're speaking of the beginning phase of a so-called "Roy Rogers" mount. If so, the problem probably relates to leaning the bike and the deflections in wheels that can cause. Try riding this way (find a shallow downslope) with the bike more vertical, and leaning farther to see if that makes a difference. I suspect that with the bike leaned more a brake shoe or possibly a tire is rubbing.

You might also try statically loading the bike thus way (use a wall to support yourself) while your wife watches for deflections at the top of the wheel.