Why would I do this... exactly?

I just give a certain girl in my class (college) a stuff toy (cat). There is someone in the class that is trying to court her. For some reason, I am thinking that I got her the stuff toy not to impress her but just to make the other party jealous (yes, I know, I am a horrible horrible person).

I like her but maybe its a crush and infatuation but I am gaining happiness just because some guy is getting jealous... although he is hiding it.

Why am I like this? Any input about my personality and should I stop scheming against him?