If the four-year old was diagnosed while she was pregnant, then it more than likely was SMA Type I. And unless one elects to have the children placed on ventilators, the condition is usually fatal before they are school aged. I've cared for children with this condition, and some families elect to not treat, letting the disease run its course and keep the child comfortable with hospice care only.
Other families elect to aggressively treat, and the child eventually becomes completely paralyzed, unable to breath or even blink.
I have cared for children in both scenarios in the home care environment. I will not comment about the quality of life in either case.
NOT excusing her conduct, just offering some information from my perspective.