[xm177e2]

The problem is that she never clearly told him to stop. Mumbling something like "I need to go home" does not constitute withdrawing consent any more than saying "I don't need to go home" is consent for sex.

[visualops]

she never clearly told him to stop

Never told him to stop, period.
There's been a fair amount of speculation as to state of mind and what 'really' happened.
I submit it could easily have been the culmination of an evening of teasing and game-playing.
Perhaps she was laughing and giggling 'I need to go home'.
Point being, if you don't want to have sex with someone, the time to decide that is not after he's got his dick in you.
One should be taught to say what you mean and mean what you say, to be responsible for your behavior, and have the sense to not party and fool around and then wonder 'geez, how'd that happen' doh!