Hard to tell exactly what you’re trying to do, but you might try putting a socket in the hand bone, spawning the emitter attached to that socket. Since it’s attached, it should follow what the socket does, so if the player turns the socket turns, and you don’t have to rotate the emitter at all, just simply activate/deactivate it.
The emitter will face forward constantly in relation to the socket, but the socket will rotate with the player because it’s attached to skeletal structure.
(You may have to rotate the socket or the emitter to get the initial vector to your liking, a proper forward vector if you will)