My partner's health condition is one of those frustrating ones that swings between flare-ups, where she is very ill and can lose coping skills due to severe malnutrition causing cloudy thinking, and remissions where she can expect a virtually normal quality of life, with just diet restrictions and meds.
Then perhaps NVC could help reduce the "volume" some when she is in a "bad phase" of her condition. And when she is in a "good phase" of her condition it can help reinforce to her that you are NOT out to get her, you will treat her with the same, kind but firm manner?
If she is capable, perhaps she can learn NVC skills too? Perhaps learning together could also help bond you better?
I don't know if there's anything local for you both in terms of "dealing with chronic patient" stuff. As the patient or the caregiver -- we get classes like that posted in our library and hospital so... maybe check those out where you live? Extra support couldn't hurt.