...why wouldn't you be able to teach her to ride? My mare wasn't broken til she was 13yrs, and she was a crazy, stubborn old bat. She turned out just fine.
Her son wasn't broken til he was 7yrs, and he did just fine too.
There's no correct age to break a horse. Horses can get used to many things, regardless of age.
And I wouldn't approach her as if she's a two year old. She's not. She's a mature, full-grown horse who ought to have learned how to process information fairly effeciently by now. Just take it slow and don't assume she's going to have a heart attack at the sight of a blanket.