Depends on the situation.
In general, if I'm being assaulted by a female attacker, I'll start with trying to escape the situation (aka, running away). Next is blocking, restraining her, or tossing her to the side and escaping. Only as a last resort will I strike her, because I know I'll hurt her if I do strike her. Again, this is a general situation.
I was raised to never hit girls; if a girl was attacking me, I should walk/run away. I believe I was taught this not out of respect for women, but out of fear of the law. If a man attacks a woman, even in self-defense, the law will usually take the side of the woman.