Yes, but here's the thing.
A rescues, so he's in battle
B blocks, so she's in battle
A is set aside, so he's not in play
B wins, so she does... um... wait... where did he go?
The reason it doesn't work with Heroes who just plain lose is that they remain in battle until the very end, and then Pot's Wife sends them to a new destination - the Land of Bondage - rather than the discard pile as the rules would state.
So in a settled loss or stalemate, she wins and captures them. If she wins by special ability, she captures if the Hero is still in the field of play to BE captured.