Keep your hands to yourself

This may be one of the most confusing things I've ever read:

Police said a Dallas woman was threatened with a knife in a fight that allegedly started when a friend rubbed her bottom with a finger. A police report states 22-year-old Laquita Mattox was sitting on her friend's bed in a Dallas apartment Thursday when her friend rubbed her finger on Mattox's buttocks.

The police report said Mattox clenched, breaking her friend's bed, angered the unidentified friend and started a fight.

First of all, the word "her" is used so much there that I'm not sure whether or not we're talking about a guy or a woman using their finger to rub someone's "bottom."

Also, how does one break a piece of furniture by, uh, clenching?

On second thought, I'd rather not know.