I’ve long believed that she took a bad fall while drunk, developed a bleed on her brain, and had to have surgery to drain it. If her injury was bad enough, I could see a six month long period of recuperation.
It all depends on where it is and how far you let it go. My father had one of these after a minor car accident as a senior citizen. My sibling hauled him off to a doctor when he started behaving goofier than usual. He recovered in a week, with no ill effects. He couldn’t remember names and dates 50 years earlier, and still couldn’t.
However, in other cases, it can be fatal.