So should I pre-emptively go to the police, or wait to see if she causes hassle?
If you are ok talking to a copper about what happened, I'd probably do it now, as she has stolen your money. Also, if she does kick off further down the line, it will be helpful to you if the police already have a record of it. Even if you say that you don't want to pursue the money, but you want to get it on record in case there are further repercussions.
Put it this way, if I was single I would call the police; obv not given that I have a partner because that is a whole other can of worms, but it's not like your carer can divorce you, is it? FFS, disabled people are allowed to have a sex life!!
I reckon she probably thought you'd be too embarrassed to go to police hub, so by doing exactly that you are calling her bluff. As madeinwales says, if she knows the police are onto her, she is more likely not to come back for more. These cunts always look for an easy mark, show them you're not one.