Making decisions for my mom, is POA enough?

No, POA isn't enough to make across-the-board decisions on behalf of your mom. You would need to obtain guardianship over your mom.

Cindy, a POA is empowered to carry out the wishes of the person. You cannot go against her decisions. No matter how delusional they are.
A Guardian is empowered by the court to make decisions that serve the safety and welfare of the Ward (person) even though they disagree with it. That includes managing money, meds, property etc.

Who told us? And why? What's that person's capacity and involvement?

More information really is needed to offer succinct advice.