Usually it's the guys who spy on the sluts who are taking a shower and touching themselves while washing. But in this case it is the vicious girl who is curious to see how her brother's friend is showering, which makes her masturbate because of how horny she is getting.
When she notices that she needs a cock inside her she decides to get in the shower and let her brother's friend fuck her mercilessly. The girl fucks him, but what the slut didn't expect is that her brother's friend cums inside her pussy without warning. That makes her angry because she might get pregnant as a slut.