Most Helpful Girl
If I were you, I would treat her intolerably. One of the following should definitely work.
1, Start blaming her for something. (It will take some time till she starts hating you. First she should realise that you do it groundless)
2, Be very mean to her (Still takes some time, can be effective, however she can also fall for you in this case)
3, Just ruin her clothes or her hair (Instant effect, but not lasting. Make sure you will be very cruel)
Most Helpful Guy
I'm not even gonna ask why you would want that...
Just be a dick to her I guess