Hitting Negi's head had the intended effect of giving Signum time to recover from the blow, though she's still going to be feeling that hit for a while. She needs to either end this or run before he can get another direct hit in, or she won't have the stamina left to fight anyone else.

So, naturally, given those two options, she charges Negi again, leading with heavy, fiery slashes, trying to overwhelm him and beat him back harshly while he's still seeing stars.