Every woman is built differently. I couldn't do doggy style till we tried it once with my arms out of the picture - instead of on hands and knees, I was on face and knees
For some reason that shifts all the relevant anatomy in a way that makes it MOST pleasurable. (And I also get to rub my breasts against our really soft sheets.) Being on top is also painful unless I'm shifted forward - can't sit straight up unless I'm very careful.
If you're really hooked on trying doggy style, just experiment (fun!) until you find a configuration that works for her. And if you can't, well there are tons of other positions out there
Good luck.