I think it's a rather harsh reflex decision for not fully knowing what may or may not have happened to someone else's ~$100+ point-and-shoot camera to write off a company's product line entirely. I'll assume you ARE either the aforementioned son-in-law, or more likely the husband of this person, not just another party familiar with these people to feel so personally injured in this particular case.
Working with electronics in my 9-5, I see so many things get broken due to misuse or lack of basic care, (in my personal life also with family, friends, etc) and the person rarely admits to what really happened, just out of a normal human tendency to not want to look foolish. You see enough of it however, and you know better, but you ask anyway, half out of seeing if they will actually fess up to it, and half out of a way to entertain yourself. I'm sure you may have a little bias of wanting to believe this person's side of the story, but like others have said, if it hasn't been in her possession 100% of the time, there is no way to be absolutely certain someone else may not have bumped it and damaged it and covered that fact up without her knowing.
I have personally dropped my Sony P&S onto a hard concrete floor, which when it happened I was almost sure it was going to be an end-of-life event, but after reattaching the doors, batteries, etc, it came right back on. I would think Canon would have similar build in their P&Ss and to cause functional damage would have to be pretty hard as well. Unless absolutely cheaply built, things really don't spontaneously destroy themselves anymore without a good reason.
I don't think that if I had spent enough money on a brand new higher end phone (ie. equiv to a 5D3, 70-200 lens, etc) from a company like Motorola, then had a support problem with a small accessory like a charger (ie. relative spending equiv to a SX150), that I would be talking about liquidating the phone, or never spending another penny, as a response.
Can you update this post when you plan on putting your gear on eBay?
5D3, 70-200 f/2.8L IS II, 200L II f/2.8, 100L, 24-105L, Sigma 50/1.4, Rokinon 35/1.4, Canon TC 1.4x III
No offense implied, and when you calm down, I think you'll come to your senses.