I don't think so.
In the particular case that you gave, the condition has gone on for a long time. It's not unreasonable to think that it's going to last for a long time. Also, to my mind, you said she doesn't want to undergo further treatment. The question really is whether we want to be a party to helping people die prematurely.
I think that, in the absence of absolute evidence, data, that shows objectively that this is never going to be treated so that the suffering can be reduced, we have to say no. I'll tell you, subjectively, that the condition isolates you. The condition lies to you, and it is simply not the truth for so many people. While you might be able to find a case here or there of there being no other way, you're going to find as many cases of people who end their lives prematurely when they could have gotten so much better.