Let me start by saying that I was(guess it shows the writing and film crew have done their job)disgusted that this happened to Sansa. To be fair, though, a lot of us had to know it was coming. We either didn't want to believe it because it was Sansa, or because we thought she was maybe finally turning into some dark "badass" that sticks up for herself. As a few others have stated in the thread already, Sansa has seen a few weddings herself and knows what is supposed to happen after. She knew that she'd POSSIBLY have to marry Ramsay and by doing so LIKELY lose her virginity. Sansa is an airhead sometimes, but she knew that if LF didn't return sooner than later exactly what she'd have to deal with.
That being said, the more I think about it(until we hear otherwise from Sansa)I'm not sure this was rape. Did she want to have sex with Ramsay? No. Does she love him? Fuck no, and this is not who and how she wanted to lose her virginity. However, thinking about it further has lead me to believe there is a chance she wasn't raped. Is it perfectly possible that Ramsay was a lot more rough with her that he could(should)have been to such a sweet girl? Sure...but I'm not really sure if that was rape. Rape or not, Ramsay doesn't care about being rough or sweet. He was born a sick and twisted human and doesn't care about anything or anyone. The only thing he ever wanted was approval from his father and he got it. Sansa doesn't love and Ramsay and he doesn't love Sansa. Ramsay knows she doesn't care for him. He's just taking advantage of the situation and fucking a beautiful woman before something can keep that from happening.