I think she sprayed him because he was becoming possessed by the devil and it was her only...oh wait never mind guessing as to why this event took place without context is a stupid, stupid thing to do that_guy.
as for weather or not the assault charges would be the same that's a tough one, he's walking away (kinda) and gets assaulted. and then after he goes a way there's an edit in the video before he goes back to hit her.
The edit and lack of sound and context make armchair lawyering this video kinda futile.