My Mother (87) had a brain aneurysm, during SNF, she's sleepy and unable to participate. Can Medicare refuse payment or she be released?

Have you asked about Hospice? Medicare will cover inpatient Hospice if you can get her admitted there. You really need to talk to the social worker and the discharge coordinator at her facility.
Our mom got the full 20 days, then another 70 days at $100 a day, then after that she had to pay $13K a month.