What do we need to ask the doctor re: my mother-in-law's sudden personality change?

by Jean
(NC)

My mother-in-law just turned 97.

When daylight savings changed, her personality has turned from depressive to talking/humming/singing most of the time while she's awake, more argumentative, and has occasionally tried to hit her daughter.

She has started to struggle with remembering grandchildren's names.

What should we ask her doctor i.e. lab tests or medications?