You don't want to insult her? Yeah, but you wrote:
"He is probably getting a kick out of trying to get my sister out on a date so he can turn around and LNAOLIHDL :IHOIHDOUMAAOOOOOOOOO all in my face about it."
Let me paraphrase how she read it:
"There's no way he could be genuinely interested in you. He is just trying to 'get under my skin' in the most disgustingly desperate way he possibly can. I mean, he's already had the originial, the best...why would he want a second hand copy-cat imitation?"
Smurf, not sure how close u and your sis are, but she's may think you're jealous from your reply.
I think ATW is right and I'm not saying that b/c he's my best e friend.