I'm not going to get into this one too much. Looks like Watermom and CarlD are giving you as much help as your MIL can stand.

But here are two points to consider:

#1 - DE filters will remove most anything that makes pools cloudy, given time. If you can run your filter 24/7.

#2 - Live algae plugs DE filters pronto. If you've still got some, you need to kill it ASAP. Doing so will make clean up MUCH easier.

#3 - It's quite easy to cause some bizarre forms of cloudiness that are hard to filter even with DE, if you keep mixing mystery chemicals. If you can 'lose' or hide the MIL's chem stash, that would probably help.