When pushing an Enemy, can it only be moved directly away from you, or can it instead be moved sideways to any adjacent (to the Enemy) unoccupied space?
It's any adjacent unoccupied space.
As a reminder too:
PUSH / SWITCHING PLACES: Switching places or being pushed
is not considered movement. Zombies will not attack players
who are moved as a result of a switch or push. Players have the
option to play a Response Card triggered by the push or switch.