A PC may (definitely don't have to) perform some kind of sexual act on themselves or on another PC in front of the mirrorDoor to avoid stress entirely and open the door. The PC or PCs don’t have to describe what they are doing if it is private. They can make the other PCs and Hannah turn away. If the act is private, have the PC or PCs either whisper the act to the GM or have them write it down and pass the GM the paper. GMs should use their digression; don’t make your players so uncomfortable they don’t want to continue.
The other way to open the mirrorDoor is to look into the mirror. This will trigger a 1d100+2d20 chart of weird scenes that the PC(s) will see. The door will open, but the PC might accumulate stress against their constitution.
This is a mechanic of the game that supports the overall plot. The dungeon is alive. It's seducing hundreds of villagers and now you. If this is unsettling, then this is not the game for you.