[Lava]

I checked the script. Make sure you stand as close to the mirror/portal in the norther part of that area, but not just with you, but also with Yvette. The script can actually detect if you are close to it. Make sure you're outside of combat. If you do that, and still nothing, just change the variable with this script:

C:SetGlobal("YvetteSpellhold","GLOBAL",3)

It should force the next scene.