That's right on topic, Nisha.
It comes down to your definition of "willing."
Example: If a girl who is not a slut has a 12 pack of beer and slurs "anyone want to f**k me? climb aboard!" is she willing? We can argue that she put herself in that situation, but the law protects her because at that moment, the alcohol has made her out of her mind and therefore unable to give consent. So the law reasons ... not that she regrets her drunken folly (that's NOT rape) but that her behavior is so bizarrely out of character that she was not behaving sanely.
Same reasons that it's rape to have sex with a profoundly retarded girl or a psychotic ... she is not able to consent because she can't appreciate the the quality and consequences of her actions in any remotely rational way.
It's a high very hurdle for sure, Nisha ... 99.99% of drunken sexual encounters are not rape. The law doesn't protect women who are simply too stupid by their drunkiness not to respond to their lowered inhibitions. But here, we are talking about a girl too drunk to get home on her own who gives in to having sex with a total stranger.
Carl.