Is a power of attorney responsible for the credit card debt that the elder they have POA over, has run up?

My mother is the power of attorney (POA) for her mother (my grandmother). Grandmother is 86, and mother is 62. Grandmother owes credit card debt to the tune of many thousands, but on her fixed income can't pay it back too well. Is my mother liable for that debt? In other words, can the credit card company come after my mother for payment just because she's the power of attorney for my grandmother? Thank you in advance for your help.