If this had occurred out in a public place where firearms are allowed...I dont see where she did anything wrong. 4 on 1 and pistol whipping is definitely a life threatening situation where responding with deadly force in kind is justice. Not a crime.
I have personally never seen a FootLocker that wasnt in a shopping mall though...and malls don't allow guns precisely for these reasons. She may also be in a liberal city where pistols are not allowed like NYC etc. She will likely face gun charges as well and be convicted.
Rest assured though: 4 thugs jump on me or mine and I am carrying the outcome is gonna be the same. Play stupid games, win stupid prizes.