Is prayer obligatory for an aunt who is mentally ill, but distinguishes between what is lawful and unlawful, yet does not perform prayer correctly?

Ataxia is a mental disorder that causes its sufferer to have confused behaviors and speech, at times resembling the sane and at other times resembling the insane. Legal accountability, including prayer, is waived for the person with ataxia, because the intellect is the basis of accountability, and the person with ataxia is treated like an insane person.