snow load on an older mobile home

by Doug
(Cincinnati, Ohio)

Hi,
I have a friend that insists on having her roof shoveled off with any snow over 6". It's an older mobile home 1966, Alpine (I think). We don't get that many 6"+ snows here in SW Ohio. Additionally, her home has developed leaks several times in the last few years, I think from people shoveling her roof unneccessarily. I'd like to know if anyone has advise on how much snow is safe enough to just leave there. The roof has very little pitch so what snow she does get tends to stay there until it melts away.
Thanks,
Doug