What did she mean when she said she was the true saint, I’m slow (づ￣ ³￣)づ

Even without her powers, she was chosen by their god. I don't know how any of it makes sense to call her imposter when they've all seen her use her powers. Losing powers doesn't mean you never had them tho? I don't know why they're so set that there can be only one saint as they never explained ...
╮(￣▽￣)╭