How do you safely cut ties with someone threatening suicide to manipulate you?

So a lot is happening this weekend. I thank gag for helping me through this. Yes my brother have a girlfriend and she knows this very well. My niece tried to cut ties with the ex wife. She still calling my niece “her daughter”. My niece blocked her on TikTok. She blocked her on instagram. She had to unblock her and make a new TikTok page. She had to make an excuse that her page was hacked. My niece woke up to text messages saying she gonna committ suicide. This followed by questions- why your daddy blocked me? -where he at? Now her and my other sister are finding themselves being used for confirmation such as “yeah we still together”. This girl has placed my family through hell. She wants to be in control while living in my brother house. She got upset that my brother actually called a realtor to take photos of the home. Now she’s threatening suicide if you leave her alone.

How do you safely cut ties with someone threatening suicide to manipulate you?
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