That goes back to her decisions. Even in fighting, (or really, especially in fighting) the ability to think critically under pressure is an integral factor in success. In order to make frequent bad decisions and still come out on top in a fight, you would either have to be quite overpowered in raw ability, or very lucky. Indeed, bad decisions can work out sometimes, but not most of the time.

Edit: Ultimately, that berserker style you designed her for is situational, just like any other fighting style. In some situations, it will work wonderfully, but in others, it is ineffective. There is no magic bullet when it comes to fighting styles.