If your ex-wife found herself in a situation where she had to go without her meds she'd certainly struggle a lot harder than with her meds. How is that any less a disability than a PTSD victim needing antidepressants to quell their unending anxieties, or someone hard of hearing needing electronic hearing aids in order to hear better?

ADHD is objectively a disability. Medicine to make it easier to deal with doesn't make the disability stop existing. Hell, there's a number of people for whom stimulants don't work, or who need unreasonably high doses in order for it to work. The existence of medicine doesn't make their disability less disabling.