Wait, does a child's disability get the parent an accommodation at work?
If we are speaking of FMLA, yes, in quite a few situations involving a young child, or an older child with significant "quality of life" limitations. However, FMLA allows a limited number of hours. It is meant to cover temporary situations, so even using it for a couple of hours a week, it would run out after a while, and coverage for the illness of someone else (as opposed to the employee) is only meant to be used on a given situation one time. You can have it denied if you keep applying for it every year for a chronic situation involving the same family member.
Now, is it good business and the right thing to do to try to accommodate an irregular schedule for an employee who otherwise does his or her job well? ... To keep that person in the workforce and in a position to be financially responsible for his or her own family? Yes, it is. It isn't necessary to give that person the moon, but if you can arrive at a mutually beneficial arrangement, it is a good thing for everyone concerned, to be able to see that when the luck of the genetic draw puts you in this position, that you can still hold down a job and take care of your own. Any one of us could, through no fault of our own, end up with a dependent family member who needs a lot of personal care, and that is also something for other employees to take into account. Maybe the position she has isn't the best fit, but perhaps there are other duties that would work out better for everyone.
PS: I would agree that if the parent of a young child is refusing medically recommended best practices in regard to the child's condition, then there is a limit to how much accommodation that would merit. All accommodations given to an employee with regard to another person's care should be undertaken with the idea that it is the best situation possible given the employee's income status. (So, for instance, if the person is an executive making a high six-figure income and carrying "Cadillac" insurance, hiring a full-time qualified caregiver for work hours would probably be a reasonable thing to expect that person to do.)