I say drop into the map a few spawnpoint entities of sorts, and whenever Shub feels like it, she can do her roaring bit, and a couple of shamblers/vores spawn in.
You could also instead of telefragging her directly, make her tougher than that, and require 3 passes or so successfully through the slipgate to kill her (each non-killing one would take you back to the beginning of the winding path).
She could also fire a projectile from her gut using the teleport_train model, which emits lightning periodically from it like the Q2 bfg and impacts with multiple explosions.
Or have her do her roaring bit, and just spawn in the general area 15 or so lava balls which come down from on high at a fairly quick velocity.