If your slave is using follow, to follow your main, it stands to reason that the slave toon will be facing the same direction as the main toon. I cannot see the slave facing a different direction, unless you back track a little, but not far enough for the slave toon to start following you again, thereby facing your direction.

Your choices include:
- Having your (wife) tank position the mob and pretty much fight it where it stands - moving around serves no real purpose and probably reduces dps and/or makes non-instant heals harder to get off.
- Anytime she moves a large degree, over move with your main so the slave ends up following for the correct facing.
- Map turn keys to each toon, for example use WASD on the main which is not passed to the slave, and arrow keys on the slave which are removed from the main's keybinds. This way, you can independently turn each toon.
- Use the Jewelcrafting Jade Focusing Crystals (40 charges, about 2g each on my server) in the slaves attack macro's.

#show Shadowbolt
/assist [target=party1] or /assist [target=focus]
/use Jade Focusing Crystal
/cast Shadowbolt