The situation that I just can't get past is she didn't know how she got to the party. Even victims who don't remember the event remember what they did that put them in danger. It's a survival response.
As young man, I was involved in a fight with a guy swinging a baseball bat. It was a quick escalation and unexpected. It didn't last long, and a I dodged well, but he did catch me in the arm before a friend and I took him down. It probably lasted 20 seconds but felt like 10 minutes. (BTW I found out a few years later, he went to prison for badly beating a woman/girlfriend.)
I can still tell you exactly who was there, the exact spot, where I was beforehand, the route I travelled to get there, the clothes he was wearing, the weather, location, time of day, etc... trauma focuses the mind like that.
Let me ask you this...
If you don't remember going anywhere with anyone, and got stupid drunk, and don't remember leaving with anyone, and wake up in your own bed, where are you ?
She knew right where the upstairs bathroom was.... because she used it all the time. She remembered explicit details about the house, but couldn't remember whose house it was or who was there.
She said she had on a swimming suit. Maybe she just got back from swimming at the Country Club, or maybe she never made it to the Country Club to go swimming. I bet Daddy had a nice stock of 'beverages' in the house to entertain guests.
Guess who was President of the Country Club she described ?