I also agree with math.
She has not said unequivocally that the girls was raped, but suggested that given what little we know, that it was possible.
Someone might give consent to sex in a context of a dating relationship, but not give consent to the same person, on the basis of a ONS. And the DD possibly changed her mind on this point only on the basis that she was too drunk to consider her actions rationally.
There is nothing wrong with having a ONS, if that is what both wanted. But the girl is somewhat confused, so perhaps it wasn't what she wanted at all.
I think sometimes it's difficult to consider these things, because it might mean we have to reassess some of our own drunken sex experiences, and we may have talked ourselves into believing they were okay, when on closer scrutiny, they were not.
I speak for myself, here. I have had willing, if drunken sex, and have also been taken off guard, when drunk, to do something I would not have done sober, or even less drunk. I now know that situation to be rape. I was very ashamed of it for many years. I thought I was guilty of "slutty" behaviour. It's actually a relief to look it in the face and realise that 1) even if I had given consent, what I did was fine, and not "slutty" and 2) I didn't give meaningful consent, so even if it had been something to be ashamed of, it is not I who should be ashamed.
Disclaimer - I don't actually subscribe to the notion that any behaviour is "slutty". But I was brought up to believe that, as so many of us are.