OP hasn't f***ing specified anything.
Scenario 1: She was unconscious at a party when a stranger penetrated her vaginally.
Scenario 2: She was unconscious at a party when a stranger penetrated her vaginally. For plot reasons, she enjoyed it.
Scenario 3: She got slightly drunk with her female crush, flirted, then blacked out - when she came to herself, they were having sex. The next day, marriage!
And we have absolutely no blasted idea what scenario OP is contemplating. Absolutely none.
It's like:"Oh hey, I'm too busy to give you details, but is it ethical to kill or eat the mammal in my living room? " "Should I take this pill from a medicine cabinet - it's a secret whether or not it's my medicine cabinet?" "I once found a piece of string. I was drunk. How long was the piece of string."
> Legal. She is of age so it's okay.
The question is underspecified - we don't even know if she was conscious, secretly horny, or ever saw the other person's/peoples' face(s)?
Or even if there's a legal system.