This might solve the mystery of why she resigned. From her speech to House:
She's hoping they won't humiliate her with further naked pictures if she makes herself politically irrelevant. I wouldn't bet on it. She probably should have stayed on and toughed it out. That said, I have a lot of sympathy for her.
Also, she needs to sue her ex-husband for everything he's got. Logically, he's the only person who could have supplied those photos to conservative media.