Teasing something about "her" is most likely going to get you "rejected" with online game! There is a diffrence between negging her and negging something about her.
"You can't spell for shit" is much more harsh than "It is soo cute how you write"
If she decides to respond it will be something along the lines of "Thank you, what's cute about my writing?"
Answer something along the lines of "I see the little girl come out in your writing"
When she responds you can start teasing and get a little sexual in your next message.
I would probably pull your ponytail on the playground! Haha...