As another Stage IV patient, I would absolutely want this IF this were my case.
As for coverage, does your MOM have a Medicare Part D RX Plan, as that is where this would be covered. IF Not, she may be eligible for assistance with the drug maker, but if she had Part D, it should be at least partially covered. She also can enroll, next October which is the next open enrollment period. But, she may face a penalty for not enrolling when she was first eligible. I would check into it now, just in case there is anyway she may be eligible through another special enrollment period.