Is She a Mini or Standard Schnauzer?

by Steve H
(Muncie, IN, USA)

Our 4 year old Schnauzer, Maggie, is in between heights for both breeds, Miniature and Standard. She is roughly 15" or so at the shoulders. That is taller than a Mini and shorter than a Standard.
She is white and weighs around 32lbs or a little more. I would love to know if she is a Miniature or a Standard. Would a DNA test help determine her breed once and for all? We rescued her from a bad situation and the previous owner might have been cruel to Maggie, she has a big bark but really is quite timid.
I have personally met three AKC registered Miniature Schnauzers, two males and one female (one of the males is a retired show dog), Maggie is much larger than all three. My wife says we shouldn't care about her breed because we love her no matter what breed she is, which is true. But, I would love to know conclusively, if possible, whether she is a Miniature or a Standard.