My daughter is POA over my mother and she is using her spending her money and being mean to her. I am the oldest child, what can I do?

We do need the answers DeeAnna asks for.

What do you mean by "being mean to her"?

If your mother is still competent to make her own decisions, she can change POA any time she wants to.

We need some clarification of your situation please. Your daughter is Financial POA of your Mother (who is also your daughter's Grandmother) and is spending her Grandmother's money. How do you know this? What proof do you have? Is her Grandmother (Your Mother) aware that her granddaughter is taking money & spending it on herself instead of on Grandmother or instead of paying Grandmother's bills? Why is your daughter Financial POA of Your Mother (her Grandmother) instead of you?