I think it's reasonable. I'll tell you my sort-of-similar experience.
I struggle with what to do about medical help with Oldest's Crohn's. The biggest thing for me was stopping helping her buy her ostomy bags. They are not optional, she has to have them. Can't function without them. I won't go into the gorey details as to why. But they are very expensive, and she is uninsured. For a long time, this was something I was willing to pay for, although they cost around $100 a month. But, she doesn't take care of herself or her ostomy site. She used to get infections often, and need antibiotics, and I'd pay for them. She would wait until the last minute to tell me she needed more bags, and it would be an emergency. She has no car or drivers license, so not only would I have to fork over the money out of the blue, but I'd have to drive her to go get them at a pharmacy (and not many pharmacies sell them, so it was a hike to get to the one that did). I looked into mail order etc., to lessen the frustration on me, but ultimately told her that she needed to take responsibility for it herself. I reached a point where I said I'll pay for 60 more days of supplies, and that will give her time to apply for assistance and get them covered. There are programs here she could qualify for that would cover bags, doctor visits, medications. She has never applied. So, after the 60 days, I stopped buying her supplies. She's found the money, somehow. She still has never applied for assistance. She goes to the ER when she needs medical care, but pretty much ignores the bills that come. There has been at least one time since that she's called me in a panic about a bag leak and being on her last one with no extras, and I have not offered help. It used to happen often, and I'd jump and help her, but no more. This is not my problem; she waited until the last minute, not me. She'll have to figure out how to deal with it. I won't be here forever, and she'll have to figure out to care for this chronic, lifelong illlness on her own. To her credit, she's doing better at helping herself (even if not taking care of herself), and she rarely asks me for help any more.
Sometimes, even with health issues, our kids have to learn the hard way that their actions (or inactions) have consequences. It may seem "mean" to refuse to help with medical care, but if it's a difficult child who is their own worse enemy who literally makes themselves more sick because of their behavior, I think we don't do them favors by enabling them then, either. Even though it's painful to watch. If Oldest were taking care of herself and being responsible and she was ill because of a Crohn's flare, I'd help her. That'd be different. But I won't feel sorry for her and help when she's posted on FB about partying all the time, and then her Crohn's flares or her bag leaks. That's on her.