I have seen first hand how a serious illness can distroy a MR. Some people simply cannot deal with a lifestyle where their S has to face sickness or some sort of limitations. I have also seen & heard of cases such as yours, where the S would stay by their loved one's bedside...but when the doctor said they were in remission....the S left. There could be several reasons. I'm sure she was scared that you would die and maybe she doesn't feel that she could go through that again. Perhaps she had to face her own private thoughts and was disappointed that she was not stronger. Some people just do not want to be around any sickness, b/c it is depressing if one doesn't know how to handle the day to day mental attitude.
She may honestly not know how to tell you what she's feeling. I would bet that she just wanted to "escape" b/c the M took on a different life from what the two of you had had and she found out that she was no longer attracted to you. She knows in her heart that she "cares" very much for you, but the sexual attraction is gone. She doesn't want to tell you that b/c she knows it would be awful to tell someone who has been fighting for his life that he is not attractive. That puts a lot of guilt on her, so she wants to escape.
Unless I missed it, she hasn't asked for a D. So my advice is to give her what she has asked and split things up and give her the space she needs. I can assure you that being a stubborn H will not make you attractive in her eyes.
Do not file for a D. But if she wants one, let her do it. In the meantime, you work on getting very healthy. You work at improving "everything" about yourself. You've been given another chance at life....so don't cheat yourself of the happiness you deserve. You cheat yourself by having negative feelings....and that is not what you need while trying to get stronger.
After some more time has passed, and she sees the man she fell in love with.....then she will begin to feel drawn back to you.
She has seen you very ill (which you could not help), but it's important that she sees your inner strength. If she sees you feeling confident of your own life & health, and sees you in every positive light....then she won't feel as much "fear" as she may have felt when you were sick.
So, leave her alone and do not pursue her. Give her time. Work on yourself and be happy. Whenever she runs into you she will see this happy man and I believe she will think you are very attractive and it will stir some old feeling within her.
It is not about what you feel should work in your M. It is about doing the work that gets the right results. Do what works!