er..this is barely passing as to how exactly this is related to MSN Messenger.
Perhaps your ages would put some perspective on this, as I get the impression that you are a 13-16 yr old teenager, but your reference to
(she still lives with her mom)
confuses me, as most teenagers do live with there parents, and don't get poked fun at about this until the age of 20+.
What exactly are you expecting for an answer here? If you don't want to be friends, be unfriendly, you can always block her on MSN if she adds you, and thats all you can do.