I;m going to confront this bully....advice?

[Jordan]

http://ca.answers.yahoo.com/question/ind...536AAWX0I5
So, basically what happened was that I had to correct her test, and she recieved an "F" on it. I wrote some comments such as "messy handwriting" or "bigger drawings" or whatnot. This was a month ago.
I found out today that she had apparently written about it on Twitter.
I decided to look it up and I found them. She wrote like five tweets about it; she was calling me "*****" and posted some pictures of her test and saying she wanted to fight me and that she was going to look me up on Twitter and "tag" me (I actually don't have a Twitter).
My school is against bullying, I'm not sure what the policies state, but I can print these tweets out and give them to the office.
I've decided to talk to her about this directly, so today I asked her if we could talk tomorrow. She looked at me oddly and laughed a bit and asked why, but agreed to talk with me for 5-10 minutes.
She posted on Twitter ""Jordan wants to have a quick word with me. Idk if i shoudl be scared?"
How do I talk to her about this?