Mom refuses anything; what do you do?

Hi All,

Wanna ask, have you ever taking care of elderly who just refuse of doing anything? Food, medication, activity, all. If yes, how do you face it? What do you do?
I'm a caregiver for my mom who is now facing malnutrition. But she keeps rejecting taking medication, activity and all. She just wants to lay on bed and sleep. What should I do? I'm sad and mad. Don't know what should I do to her. I have been trying to talk to her with no result.