I agree, cut her off and call the cops when needed.

By setting firm boundaries you are actually doing her a favor. You are being a good role model. If she shows up at your door, tell her to go away, if she does not - call the cops. If she threatens suicide, call the cops.

You have the right to your own boundaries, choices, and decisions.

She may initially respond with increased drama, expect that and be prepared. What you can control is your own actions. You can prepare short statements that you can say, stick to your decisions, don't let her engage you in conversation. Be ready to call police.

Sounds like she is relying on people feeling like they have to be "nice". She is treating people very badly. Firm consequences will help. You'll get to set your own boundaries and defend them if she keeps trying to break through.

Keep records of everything that happens. This will help with any police reports you might need to make, or even a request for restraining order. Keep records on each time you tell her to leave you alone and each time she hassles you.

Good luck!