I agree that her inevitable demise will leave her family better off in the long run, and will probably come as a relief to them.
However, short-term, Clotso is going to be a burden in death. I hope she has saved up for her own burial expenses, which I know she hasn't. It is unlikely she can be cremated; I don't know about Canada, but in the US, 260-280 pounds is the limit most crematories will accept for cremation. And with good reason; crematory chambers have literally exploded, and crematories burned down from trying to cremate deathfatties; grease fires are no joke at all. Insurance companies frown on cremating bigger ones. Finding one willing to take on 400 pounds of compact fat is gonna cost a lot extra, if it can be done at all.
So: it will probably have to be a burial. Problem is, she is too fucking fat to fit in an ordinary casket, so she'll need a double-wide. And that means, she'll need a double plot. In Ottawa, we're pretty much looking at around $5000 Canadian to plant her in the ground with little fuss. If you want a funeral to go with that (they may just decide to skip it), add another $1000-$2000.
It's not as much as a new car costs, but it is still a pretty hefty bill to get hit with suddenly. I suppose they could go the potter's field route.
If Chantal really wanted to do "adulting", she'd take out a life insurance policy and name her mom as beneficiary. Or, at the very least, sock away six or seven grand for when the big day arrives. But she doesn't care. And she won't care when she's dead, either.