Nah, she'd probably be fine. Self defence is based on the honestly held belief of the person of what they're experiencing, regardless of whether that belief is accurate, and whether the force she has used is reasonable and proportionate.
Her honestly held belief was that her life was in danger and that she had to protect herself.
Her honestly held belief was that the intruder was going to kill her, so she responded reasonably by using the same/proportionate level of force by hitting him over the head.
However, had once she had hit the intruder over the head and they were unconscious, had she continued to repeatedly hit him over the head and smash his skull in until he died, then it's more likely it would be murder, because she no longer would have been acting in self defence. (Because it's not self defence once they're unconscious)