no leave it completley.

stop obsessing over this one girl and get over it.

she rejected your friend request. so what? she probably thinks you're a loser or doesn't know you. move on.

everyone treats FB differently. some people will accept anyone, others only like to accept people they definitley know or with display pictures because loads of random nerdy needy men like to try and chat them up online.

just chill and start talking to girls in real life, leave the internet for now. don't start trying to think of a thousand amazing openers you can throw at her which will guarantee a response. that is needy and obsessive behaviour with a slight hint of being a stalker. that is NOT attractive, to a girl or to a person... and it shouldn't be to yourself either.