The problem with this argument is that i had no intention of hitting the woman. And if she had hit me there is no way the police would have charged her. I would have been seen as the blame of the fight, being the man. But like i said, no charges would have been pressed. it is a hypothetical argument. i wanted a scrap but the man said no. and no means NO! If it had been forced, then a forced result would have happened. Aikido teaches self defence. that means block when hit. or move out of the way. I cannot win a fight against the world if no-one is on my side.
I would not recommend fighting the world because it's pretty big and the odds are against you
. I also think that some people are on your side in regards to this situations. Ultimately this is your decision to make. You are both adults so if you want to have the fight with the girl then we can't stop you but just be ready to accept any potential consequences that come along with it.
Have you explained to your instructor that you would like to test your aikido? Maybe he can come up with a workable solution for you. I can't speak regarding legal issues but in my opinion doing this in a dojo (with your instructor's consent) with other people around is better than going out on your own to do it. At least with other people around they can step in if things go to far.
I've gone to my instructor many times and have asked "how would you handle something like this" and I've had students coming to me asking the same type of questions. We've always worked through it to figure out a solution, even if that means finding a wrestler, a BJJ practitioner, or a boxer to come in and work with us.