I'm going to report a classmate's rape but for selfish reasons
How will you do it for selfish reasons?
I'll be dating this classmate after she was raped
Even if you are doing the right thing it is not good to do it for the wrong reasons. It can make the person feel bad to know that you don't really care, you just want in her pants.
I don't care what you think, I will do it.
Your motives here are impure. You should report it because it is a crime and not because you want to get with her. Stop trying to take advantage of victims.