Hi Shedd
I'm sorry to hear you're having these thoughts, and about the physical state of your ex.
Are you seeing a counsellor/therapist? When struggling with this kind of thoughts and feelings it can be of great help to talk to a professional. It can be hard to break that type of thought pattern on your own, and as you say, your ex isn't ready to listen to you. I would advice you to look into seeing one of the above, if you're not already doing so

I hate to sit around watching her die
I understand you feel upset over seeing her in this state. Now, we're not at all sure it's actually going to lead to her death, right?
and not be able to do anything.
... .you're right. And for me, accepting that some things in life are impossible to change hasn't been easy. But it can also be of comfort as you gradually embrace it, meaning you can then relax from that and focus more on yourself instead

Am I making sense?
Can I ask you this:
For how long have you been separated?
Do you see her on a daily basis through your work?
/Keef