Could Kreese have had something to do with Tory's mother death?
The doctors said she was doing well and Kreese was desperate for her to rejoin Cobra Kai. I suppose it's possible the doctors didn't catch whatever it was, but it could also be possible that while it would have killed her eventually, it wasn't enough just yet.
The thing that convinced me was the mother had her hand in a fist shape, like she was going to strike.
Of course Kreese couldn't be sure Tory would run back, but it would throw her off balance if she didn't return.