This girl had the worst thing happen to her - she was trying to take a selfie, thinking she was all alone, when her roommate walked in. To make things worse, the girl wasn't doing anything shameful, she was just trying to pose doing a peace sign with her hand. Yet, since she overacted when the door opened, her friend thought that she was trying to masturbate or do something weird on video.
That's why everyone is so freaked out in the photo. What happened next is that they either had an awkward conversation or just decided to never talk about what happened that day. Most people would probably go with the latter option, since it is always easier to forget and never talk about weird things that have happened to you, rather than to keep on talking about them.