It does sound more like fear of something rather than being cold enough to shiver at 60 degrees. It wouldn't hurt to put her in jump suits this winter and a jacket over it when you take her out. My foster, Belle (Shi-Tzu/Maltese) has cushings and very thin hair so I had Cathy (107barney) make her a silk jump suit. She even put her name on it. She makes them in different materials as well.
Washable and reusable dog and puppy pee pads, belly bands, and diapers at T. Bumpkins & Co. Cathy is a super nice gal and so very easy to work with.