
Sure looks fat to me.
As for white hair I assume you're talking about this pic:

Stanton was 41 at the time of the assassination.
The woman in the pic looks like she's in her sixties.
Any chance her hair was a different colour when she was twenty years younger?
Also, note the hairline.
According to her family, this picture was taken just a few years after the assassination happened. Her relatives confirmed Stanton had light hair and weighed well over 300 pounds on the day of the assassination. The Prayer Man in no way resembles a 300+ pound fat woman with light hair.
Do you actually think the Prayer Man is well over 300 pounds like Stanton was?
Buell Frazier stated on several occasions that Sarah Stanton was standing to his left. He never said once that she was to his right. Frazier said he was standing outside just a few minutes before the motorcade passed by.
How would Stanton be able to move all the way over to Frazier's extreme right in just a few seconds time while he was still in mid conversation with her?