She won't be a US 16 as that's a UK 20. Hence Vanessa Feltz being confused about being a size 12 in Gap when their jeans are US sized.
SHe looks fab and very trim. If she is a 16 she is a very firm and toned one. Most ize 16s are rather more wobbly IME, having been a 16 at various stages. She is also tall ish and so a 16 is not going to look huge for her frame.
And she's probably been airbrushed within an inch of her life as well