My guess is that the mom is NOT in on it. Reselling used goods in the funeral industry, while not common, isn't unheard of either.
There was a cemetery near Chicago that had a major scandal a few years ago. Basically, they would resell grave sites after a number of years. Sometimes they'd just bury someone on top of someone else, sometimes they'd dig up the old grave and toss the old body in a mass grave, and sometimes they didn't get around to making a new mass grave. IIRC, it was discovered when someone went to visit a family member's grave after a number of years and couldn't find it.
https://en.wikipedia.org/wiki/Burr_Oak_Cemetery#:~:text=2009%20scandal,-Incident&text=On%20July%2011%2C%202009%2C%20Cook,back%20at% 20least%20five%20years.