[color:"orange"]The problem is that she had gone downstairs before her second summoning and now the stairs have collapsed and cannot go down them.[/color]
This is in the mushroom cave originally sealed under a rock in the burnt forest? Once the collapsed stairs seal you in the second level of the cave, you can find the yellow bafflimiri mushroom and a crystal fragment, as well as stairs back up (in a locked room). After touching the crystal and being summoned, you get returned to the locked room, where you can use the levers to open the door, and/or take the stairs up to leave.
If your girlfriend left the cave using the stairs, she can return that way by heading to the south east room on the first level, rather than the collapsed stairs in the northern room. If she left by teleporter stone and didn't leave a teleporter stone behind, or at least unlock the doors first, then there are a couple ways to get back into the locked room with the stairs:
hex teleport or use the procedure in the topic
armory trick in act 1 to get a summoning doll into the locked room.
BTW, complete all other quests before giving the ingredients to the alchemist.
