That happened to me. Really. When I was in 7th grade, an 8th grade girl sucker-punched me in the stomach (to this day, the hardest hit I ever took - she was taller and stronger than me) for "saying something about her" that I never said.
Frankly, I didn't even know her name. She was a whack-nut.
Anyway, after I caught my wind, I got up and slugged her back.
Guess who got suspended.
I hope you hit her hard enough to deter her from further sucker punches. You don't mention that she hit you again.