She robbed him before, robbed him again and broke his collar bone, she might have come back a third time, armed and with a vendetta....but now she won't be bothering him again.
Say you've been robbed a couple of times and got the guy on camera. Later you are walking down the street and you bump into him. Do you get to shoot him, because he might come back again?
For valid self defense the threat has to be imminent, not hypothetical or in the future.