How can you convince someone from sitting on the bed to laying in the bed?

Going to bed at night from either the living room or bathroom, Mom sometimes wants to sit on the bed without going to bed. Sometimes she doesn't think its her bed even though there is a sign saying that it is her bed.

Could you put a lot of pillows behind the person's back so they're half sitting/half lying down and then the next day, take away one pillow and the next day take away another one, etc.? Would something like that work?

Can you give us more information? Does the person have trouble breathing when lying down? I would think elevating their head may be the middle ground that might work...but tell us more about what is going on please.