My friend keeps messaging me on Facebook?

[Samantha]

So my friend, Jamie, keeps messaging me on Facebook, the reason I don't reply is because we have nothing in common, so that makes the conversation really awkward, and 99% of the time I'm busy! This is how the conversation goes

Jamie: Hey Samantha
Jamie: Hey
Jamie: Hey Sammy
Jamie: I know your on Facebook

* then at school *

Jamie: Hi Sam

Me: Hi

Jamie: Why were you ignore me on Facebook yesterday?

Me: Because I'm busy

Jaime: You could have just said so, jeez

Me: I would have, but look at how you just reacted, your so sensitive!

Jamie: Me? Whatever Samantha, stupid Sammy.

Stupid Sammy? Um okay then, see how sensitive she gets? She is always so clingy to me especially in the hallways when I'm with people!

Jamie: Who's that?

Me: My friend, Noah

Jamie: Your boyfriend looks cute

Me: He's not my boyfriend

Jamie: HEY NOAH! SAMANTHA SAYS SHE DIGS YOU!

and she just embarrasses me all around school! I like Jamie and all, but she is just so annoying! How can I just tell her to knock it off or even avoid her? Were in the same class for everything!