I think the line about her not being physically harmed was meant to tell readers she wasn't raped. If Rowling wanted to imply differently, she could have just kept that sentence out. It's not like eleven years olds would have suddenly cried "Rape!" if her physical appearance wasn't described.

I'd also say it would be pretty damn obvious what was wrong with her if she'd just been raped by horses.

 

They came inside.

Enter the story:

"19 Years Later: The Umbridge-Firenzes"

 

Two words: "Vaginus Reducio!"

Or, if you prefer: "Tergeo Cumdumpster-o!"

Wasn't there a follow-up scene (maybe a movie outtake) where Umbridge sneezed on Filch, and Filch asked her how much curdled milk she'd drank?

/bad attempt at humor

Seriously though, I like to think that ol' Dolores *did* receive the centaur-captive bonus plan of hot beef injections. I just despised that cunt so much while reading that book that I can't think of any fate too bad for her.