If they did just rape her (I think it’s not clear whether they actually raped her), at least I could understand their motivation.
What we know they did was strip her, draw on her, stick objects in her, and take pictures of it to humiliate her. Nice “joke” to play on a “friend”.
“Nice joke to play on a friend.”
No sh*t...
Shaving a head? Ok.
Drawing a mustache with a Sharpie marker? Ok.
Sexual battery? Uh...no.