It must have been daunting, I’m sure you shat your pants first time reading I would have probably done so too, we all try and keep those two lives separate and the unthinkable damage that it could do if they crossed is Terrifying.
All the recommendations are correct so far and it seems you’ve taken the right approach.
“Now demanding £1000 in cash” - In cash, trying to make it untraceable. Like also said before, it would not stop if you gave in, she’d get that taste of cash and milk you till kingdom come.
Definitely report to police, fight fire with fire.
Glad you posted her link, maximise the exposure on this, she could be doing this to multiple people!
Can you post the number so she can be tracked that way also if she pops back up?