I never did figure out where I made my mistake in flipping all the required plot flags for this quest, but if you encounter the same problem, there is a sneaky way around it.
1. Enable debug mode by adding the following line to Baldur.lua in C:\Users\[Your user name]\Documents\Planescape Torment - Enhanced Edition\
SetPrivateProfileString('Program Options','Debug Mode','1')
Talk to Vivian and she will give you 25,000 experience and a permanent +1 to Charisma by extracting your "scent" (aka all that embalming fluid in your body).
Then you can talk to Marissa and return her veil to her for another 25,000 experience.