She did the right thing as the outcome shows, I don't see what else she could or should have done
No. I would have told her whatever she did was fine, because she was there and I wasn't.
If she asked the cop for help, that was fine.
If she gave the guy money, that was fine.
And if he's laying dead with a full magazine in him, that's fine, too
You would have thought it was fine if you daughter shot someone for approaching her something that she could end up in jail for.
PS I doubt if similar happened to my wife here she would even tell me as she would not see it as threatening.