I would say no. She is an adult not living in your home. You would have to prove your taking her to Dr. Appts and buying clothing constitutes over 50% of her income/care. She must be on Medicaid. Her SSD cannot be enough to pay for a NH. As such, Medicaid is paying for her care. She should have a personal needs account that she can use to offset the cost clothing when needed. They don't need much.
Now, if you have kept good records, you may be able to use the clothing and mileage as part of your deductions. But that is a question for a good tax preparer.
No you can’t. And not because she doesn’t live with you, she doesn’t have to live with you in order for her to be a qualifying relative dependent. It’s because you aren’t providing at least half of her financial support. You will never get away with claiming her because shes in a nursing home and on Medicaid. Her monthly disability check nowhere near covers her room & board, it pays a fraction of the cost.
To claim your sister as a dependent relative, you have to be able to document that you pay more than 50% of her support. I wouldn't imagine that clothing and transport are anywhere near 50% of her total costs.
go to the IRS GOV website and read their definition of dependent for deduction purposes,
Now, if you have kept good records, you may be able to use the clothing and mileage as part of your deductions. But that is a question for a good tax preparer.