Did she file an income tax return in 2018 or 2019? If so, it should come to the address on the return.
BUT, did you or any of your siblings claim your mother as a “dependent” on your 2018 or 2019 return? If so, she is not eligible for a stimulus check!
Does she receive SSI or SSDI income on a card? If so, look for the stimulus check to arrive there — and it still could — unless, of course, she was declared a dependent.
And if she did not file a return, and does not receive any government benefits, she needs to file for that stimulus check at this link: