Here's the update - she did.... (drumroll).... NOTHING!
She wussed out. She was afraid they would come back and "get" her for it in some way, so she just didn't do anything. I kept telling her that the cans of Raid would be a no-fault thing, because it's such a non-specific thing, but she was afraid.
They moved into their new apartment Saturday and they're out of the one with the bad landlord/realtor, so it's all over. But thanks for the suggestions all the same.
Keep wreves in General Talk in 2011!