I think the smoking was the problem and she probably did a lot of drinking as well. I assure you that is just a guess and I have no knowledge of that.
All I know is that my sister and I sounded just alike before 20 years of extremely heavy smoking and drinking gave her a whiskey tenor; not as bad as Susan’s but ...
But she was still the Best Person I ever knew.
I have a freind with a voice like that. She had acid reflux really bad for years. Her Dr. told her it was the reflux that caused it, and she smokes.