What I hear/read is that she engaged the guy and advanced on him while yelling "Surrender!" and firing. If a reliable and more detailed account is available, I'd love to see it.
It MAY not be accurate to say she NEEDED all ten shots. I can imagine in a situation where you are advancing on an armed person who has already started shooting that you focus on lining up your front sight with his general outline and pull the trigger until all you hear is "Click, click, click." (So why did she have only a 10-round mag? Who knows?) She may have kind of forgotten to stop shooting until she ran out or the guy was obviously on the floor and more or less motionless.
Your average LEO or security person doesn't get a whole lot of practice dealing with major adrenaline dumps. I don't think it's within reasonable bounds to expect Dirty Harry-like cool and deliberation from such folks. I think she did fine.
Are there any indications she hit anybody else? From one account that I heard, she did a lot better than her two male companions who sat around and dithered while she actually engaged the bad guy. Yeah, I guess she wasn't perfect. I kind of like her imperfection and would like to think I'd do as well in a similar situation.
There is also an account that he was wearing some kind of flak vest as well. If that’s the case, probably wouldn’t have mattered what weapon she had, it would have taken more than one shot to the chest.