Well Kerrigan doesn't have enhanced strength anymore but she is the type to get up again even after getting slammed through a wall. Assuming her legs aren't broken anyway.

You want to have them run into each other and work it out beforehand, handwave that, or they just head into battle and Kerrigan decides on the spot that she ought to back him up because hey, he's going after Yavek. That's my kinda guy.