Can unsigned waivers hold up a guardianship?

I am nearing the court date for guardianship appointment of my sister who is 58 years of age with multiple mental diagnoses that have progressively become worse over the past 20 years and became full blown when her marriage ended in divorce several years ago. She is on 7 psychotropic medications, several of which she takes 2-4 times per day.

She drives, God help us. She doesn't keep food in the house and has very poor hygiene, and is in and out of hospital because of exacerbation of symptoms and not keeping her medications straight. Her sons are basically estranged but love their Mother; they're just confused and hurt by all that has gone on over these past years.

I have the statement of expert evaluation signed by a licensed physician and agreed to by my sister, POA, HIPPA, which my sister just this weekend told me she was going to revoke (she's done this with every family member she's granted it to over the years, again related to her gradual mental deterioration) with my attorney. However, my attorney now tells me she must wait for the waivers sent to my sister's sons to return. I do not know what language was in these waivers but thus far there has been no response from any of them. Further more, before this whole process of MY involvement began we ALL talked and agreed that none of them wanted anything to do with taking on the responsibility of guardianship. Now, I can't get a return call. Could there be a concern on their part that Mom may have some money in her small estate from the divorce that they think I might get? Greed, unfortunately runs deep in this branch of the family, including my sister. I don't know. If there is any money left after these past 3 years I want to use it to help pay for her care in facilities that offer more intensive and extensive treatment with the hope that perhaps she may be able to live on her own again.

So the bottom line is this: Can the lack of these waivers hold up the proceedings of going through with guardianship?