What's the best way to deal with annoying Christian girls towards me?

[Nitro Zeus]

Today in economy class when the teacher taught us about management, banking, stuff like this. And a Christian female classmate wrote on a paper, "do you want to be my Valentine?" and I didn't know how to answer, and I ought to answer in a funny way like: "My name is not Valentine" but it turns out, that my joke has terribly failed, and she has called me stupid.

And my Christian female classmate gave me a idea to write "I love you", then she told me to forward this to her, and then she told another Christian girl: "hehehe, he has left you:)))". And I I pretended to be pissed and we're pretty much cuddly:))) and then all sudden, another Christian girl from my back has woke up and she suddenly pick on me for no good reason until I got really pissed at her until I told her a warning: "wait, so that you'll see what you'll get in break time, you'll get really harmed".

1) How do I deal with this kind of girl in my class who likes to irritate me for no reason in Islamic point of view?

2) Is there a strong supplication or chapter in which I ask God To Make any person I want, to completely forget as if it never occurred? Because, right now I really feel stupid for the answer I gave...

Please don't judge me, I just did not know what to do or to react in this kind of situations.