I'm going to tell you something hard. People who actually kill themselves rarely make threats to do so or make half arsed attempts at overdoses and cutting for months in advance. They just do it and it usually comes as a massive shock to those around them. Often the very first time their friends and family discover their loved one was suicidal is when the police come knocking. Trust me on this.
She is using these threats to keep you on the leash and eventually reel you back in. It is a classic manipulation technique. It is emotional abuse.
Block, delete, change your number. Do it now.
As PP have said, get in touch with Women's Aid. Learn about co-dependency, gaslighting, emotional abuse and control.
As you read, you'll hear bells going off in your head. You'll recognise her behaviours, tactics, even phrases she uses. It is absolutley staggering when you have these realisations. It properly floored me!
You are not alone, you are not to blame and you are not going to feel how you feel now for ever. It will get better.
You have done so well in leaving. It's a massive achievement, huge. Recognise how far you've come and keep going. If this was a marathon you'd be at the 14 mile marker already.