Wow. This is horrible, and I'm sorry you're going through it. The thing is to stay calm, and it will be key to your explanation for what happened being taken seriously. Do you have a record of assaulting people? i'm guessing not, since you do still have your career and have not already had it ruined by anything like this. That is another key factor here, it sets up whether this could have been an accident or something that you have repeat offenses of in the past. your explanation, to me seems quite understandable and valid, I see no reason why the judge won't see that. Thing is, maybe the nurse overreacted, considering, she's hormonal and pregnant! That's quite a real possibility too. It could be that will come out too and the judge might see that! I mean come on, your sunglasses? It already sounds like her story is pretty far fetched, that is, if you are being as accurate as you can in your post. I can see a very good chance that this could turn out ok for you.

Try to see those things and analyze it objectively. The severity of the assault will matter also. Obviously if you broke her nose, her rib, endangered her baby or otherwise left a scratch, I'm guessing you would have mentioned it. If she's not been bruised or damaged, how will she prove you "assaulted" her rather than accidentally made contact with her in protecting yourself?

Just some thoughts, hope this helps.