Well...
I don't know.
I once told my daughter that if anyone was ever bothering her to take the proper steps such as tell an adult, tell me (so I could perhaps contact parents and raise holy hell...) or if she needs to defend herself, then she has every right to take any step necessary to protect herself (as a last resort, of course...)

I don't condone violence, but I have a feeling your daughter had just 'had it' at the point where she struck the other girl. I guess you can be patient and 'turn the other cheek' only so much...

Is there a way you can contact the other parents and talk? (Though it could cause more strife than not...)

Is there maybe a way you could monitor what goes on at the bus stop, even if you are perhaps out of sight so it's not 'embarrassing' for her? If you know any other parents, maybe you could put together a group where a parent is present at the bus stop to thwart any misbehavior and bullying. Trade off days or something.

Certainly a tough situation. In my head I was thinking 'good for her (your daughter)...' when I read your post.

I don't like bullies.

I would probably talk to the bus driver, and see if it is going on on the bus as well...then that way he can report it to the school, with you being able to stand in the shadows of all of it.

However, if it only happens at the bus stop itself, it sounds like you may need to make your presence known and talk to the parents of the other girls.

Use the school. The counselor, the principal, etc. Have them talk to you daughter and find out if this is "ongoing" which it sounds like it is. It sounds like the school was fair in doleing out punishments, so they should be in this too. then, talk to the bus driver to see if he/she can keep an eye on it. Have your daughter sit in a seat near the driver. There is a camera on board recording at all times. If ever something goes down on the bus, have your daughter tell you or her teacher and the principal can request the bus driver's tape to identify the situation.

Talk to her about trying to use the resources around her, but don't punish her for hitting, it sounds like they deserved it (though I wouldn't actually tell her that :)
Good luck to you!

As far as the hitting, I would just say, well you know hitting is wrong and doesn't solve problems, and leave it at that. She's only human!
I think it's time to involve the school and the other parents. Put pressure on the school to involve the other parents - don't try to contact them yourself. You never know.

I agree to get the school involved, however, if she's hit, she's within her rights to hit back, IMHO.

My little man is nearing black belt level and they are trained from day one to always try to resolve disputes peacefully. They are also told to NEVER EVER be the first to strike - ONLY IN SELF-DEFENSE. With that understanding, use your karate and training in self-defense or, obviously, in protection mode of a loved one, etc. Basically, responsibly.

He has our full support if he's in a position to HAVE TO defend himself, even at school, especially against someone bigger.

Maybe I'm off base and not very PC, but I will defend him with my last breath if he's in trouble at school for defending himself.

Maybe once he gets a little older and reach black belt, those bully snots will think twice before crossing him. In that situation, it will be time and money well spent if it saves him later grief from bullies.