capacity to give consent of a person with mental retardation

can someone please help me...
we have a property,
yung title, under name nmin magkakapatid,coownership
we applied for a loan, but it was put on hold..
one my sister has mental retardation, the bank told us na kelangan yung judicial order na may maasgin na guardian so that she can give consent...
d daw pwede affidavit...
eh matagal po yun.. mg 1 yr na wla pa ren nangyari sa case...
we need the loan kse...
pwede po bang she could sign special power of attorney na lng... the bank cant question po it dba... or pwede ba nilang d tanggapin yung special power of attorney... plan ko po kse is gwa kme mgkkpatid na special power of attorney in favor of my brother... pra mabilis and no need to wait for the judicial order for guardianship...

Nope hinde po pwede yung SPA.

A person with infirmities is incapable of giving consent, so useless rin yang SPA na yan kahit pa Notarized yan ng Lawyer or even The Chief justice of the SUpreme COurt, hinde uubra yan because the document/contract itself is defective.

You have no choice but to wait that judicial order of guardianship.

ahhh hehehe.. hayys i was trying to work around it... even thinking of prng gwa na lng kme deed of sale or mg quitclaim sya... but then again wla ngang consent pa ren...
any way thank you po tsi ming choi... interesting name hehhehe