Are five shots enough? Yes, unless they aren't, as in this case.
And by extension, why would you need a hi-cap magazine? When just 10 rounds aren't enough. What if there were two criminals? What if she had pulled the trigger one more time? CLICK! Would he have come after her? My wife keeps 15 rounds of 9 mm loaded by her bedside, and I hope that will be enough if she ever needs it.