She did, she smacked the driver in the face. If she kept coming at him I could see it as self defense. But since she had backed off and he came up and hit her, I don't see it as self defense.
That might not be applicable in Ohio.
They have the 'Castle Doctrine' or the 'No Duty To Retreat' Law, which protects anyone who uses deadly force to defend themselves or another person from any civil liability against the person who created the threat against whom the deadly force was used.
Now, that's applicable to your house and vehicle, so it might or might not work in the case of someone's workplace, but the bus driver could possibly still argue Self Defence by 'necessity' or 'duress', as it is an 'affirmative defence' for attacking his attacker, even though she retreated slightly as he got out of his seat. The thing is that, she didn't necessarily leave the scene and chase her down to hit her. He got up, faced her, she remained, and after being hit once by her he could argue that he felt the danger of an attack was still present even after he got up, so he defended himself, and his passengers from an obvious violent and disruptively belligerent passenger.
I reckon there could be a case, but i'm no big fancy city lawyer.