I am POA for property....when mom is declared incapable to make good decisions. How to get the declaration?

Our POA says when I determine and her doctor determines. I'm assuming if mom goes along with everything I say about reducing her financial risk, then I don't need a doctor to declare her, correct? I only need to bring her doctor in to declare if mom is unwilling to go along with the needed changes? Or should I just go for the declaration and be done with it?? Thanks for your thoughts.

Issues at hand are credit card risk (she's overspending ) and home catalog shopping problem, buying another person a vacation, etc.

Someone kindly mentioned guardianship but I'm interested first in invoking the POA if necessary.