She had a stroke while helping plan her daughter's funeral.
http://www.latimes.com/local/lanow/la-me-debbie-reynolds-ill-20161228-story.html
http://www.latimes.com/local/lanow/la-me-debbie-reynolds-ill-20161228-story.html
Anyone not familiar with Debbie in her heydey should watch Singing in the Rain. You get to see where Carrie got her sass and humor from, and you get to see the very talented Debbie keep up with Gene Kelly and Donald O'Connor in dancing.Not surprising. Not too many people remember Debbie in her heyday, though.
I suspect that the sight of her daughter on a ventilator probably pushed her over the edge.