I'm planning to ruin my classmate's presentation and eventually her grade
Why on earth would you want to do this?
I want to upset her because she's my rival.
You shouldn't take revenge on someone. the teacher in class will see you ruin the presentation and you will get in trouble.
What does it matter, I'm going to do it anyway.
If you want to you should just try harder to beat your rival. Cheating just means you are worse, you should be able to do better on your own. Revenge can also spiral out of control and just cause you more problems than you could anticipate.