Wow, what an unstable inhuman bitch she is - total monster. This whole thing must be triggering a huge weight and turmoil of emotions (hug).
But, there is nothing wrong with you, the further she goes, the clearer it gets to Everyone that the woman is an agressive, using, cruel and unbalanced bitch... This is Nothing to do with you anymore (if it ever was, which seems tenuous), this is her being challenged on being a cruel abusive monster.
It's like all she knows what to do is to up the ante and keep screaming and bitching and bullying... But it's not working and it's not going to work. I'm really proud of you, because you aren't crumbling, you aren't letting her treat you like her slave, even of you want to just hide and be quiet and give in ... That makes you even more amazing.
You are doing the right thing, you're saying NO to her and telling the right people so they can protect you and stop her. Please please keep on with this, tell the police again tomorrow, tell your boss, and you know what would be so great for you... Tell the other nannies, those that have contacted you, try and take that first step and reply to them... And keep posting on here. Surround yourself with the good guys, it will help you see that people like her (or your h) are not going to win, she is going to have to go away, and her life will be worse for it.
What does she think it's going to accomplish? She's destroying her future by behaving like this - she is doing this all herself so don't please don't feel guilty.
Good luck tomorrow OP, keep doing what you're doing x