All of your comments are correct, however you're misapplying them to this case. No one who's fully incapacitated may give consent. However intoxication, even a high level of intoxication, doesn't preclude consent. In fact, in her condition we would want her to consent to a good cabbie taking her home.

We know that the complainant was competent enough to give consent when she entered the taxi. At some point between then and when she was seen 11 minutes later by a police officer, she became incapacitated and could no longer have given consent. However prior to that point she could give consent and, crucially in this case, she couldn't recall if she did or not. 

Being highly intoxicated, or even unconscious, doesn't change your rights one iota. But it severely impacts your own ability and society's ability to protect your rights. The primary moral of the story is, if you're going to intoxicate yourself to the point of stupefaction, do it in a safe place.