She shoots up, and it hits the alien. We don't actually see it hit the alien in the head, but it did hit it, I admit. Then it falls on her and she's shooting randomly. Again, we have no idea if it hits the head or another part of the body or if it missed. Then she pins its head against a wall and shoots it maybe 4-6 times. So yeah, it got hit a lot, but 1) the rounds are small and have poor penetration (yet it is quite a bit of force, I admit) and 2) we don't know how many ACTUALLY hit the head and how many missed or hit the body.