Permanently and totally disabled. A person is permanently and totally disabled if, at any time in 2021, the person can't engage in any substantial gainful activity because of a physical or mental condition and a doctor has determined that this condition has lasted or can be expected to last continuously for at least a year or can be expected to lead to death
If she is permanently and totally disabled she will still be eligible for EITC when you claim her as a dependent.
Since she is over the age of 17 she will not be eligible for the Child Tax Credit. However, she will be eligible for the Other Dependent tax credit of $500 when you claim her as a dependent on your tax return.
You claim her as your dependent Child on your tax return and indicate that she is disabled.
