Happened to me in my previous relationship. She brought sleeping pills, threatened to come in front of a train. The thing is, and I am sorry if I sound insensitive, but those who threaten, won’t commit. Just get a backup of all the messages, call recordings, and make sure you are clear that why you are breaking up. If possible, get her to confess that she is toxic and does not deserve you.
And no matter how she tries to convince you, or provoke you, don’t abuse her or be rude.