Your power of attorney is worthless. Unless you had a court ordered guardianship, you have no authority over your granddaughter. Powers of Attorney can only be granted by adults, and for themselves, provided they are of sound mind when granting the POA. Sorry.
I concur with attorney Goldstein-sorry.
Keep your hopes up-maybe they will consent to a guardianship.
The answer given does not imply that an attorney-client relationship has been established and your best course of action is to have legal representation in this matter.