presumably a woman can still give consent even if she is drunk
It depends how drunk. You can't sign legal documents when drunk, or consent to medical procedures, so why is the idea of 'too drunk to consent to sex' so difficult to understand?
she would never have done it if she was sober
This is not the same thing as too drunk to consent. In fact, it is irrelevant and unhelpful.
Example: I have sex with DP when sober. One time I was too drunk to consent, so we didn't have sex (ie he didn't rape me). The fact that I might have chosen to have sex with him if I were sober is totally irrelevant. In that particular instance, consent could not be given.