You said it yourself, she's educated/intelligent and busy. I'm sure she has options when it comes to men. Maybe the typical American dream for women of being a kid factory and tied down to some nikka doesn't appeal to her.
Stop thinking just because someone isn't married that there is something is wrong with them. There's plenty of married folks who are fukked up people.
I know I did say I could be wrong and that I hoped I was. Geesh gal/guy. Who took your last stick of gum?