I've never heard of a hospital discharging a patient before they are ready for rehab. There are lots of uncertainties now among Medicare providers that due to proposed cuts, they
will not be paid for services rendered. This hospital may be afraid that they will not be paid for your grandmother's stay.
I recommend that you contact Medicare immediately, 1-800-MEDICARE and ask about your grandmother's benefits. Second, speak to a hospital representative, such as an official in the discharge department, and ask if this is legal. Third, talk to someone at the rehab facility where your grandmother will be taken. Find out how long she will be there before they can begin therapy and apply for Medicare reimbursement.