She wouldn't have been so specific at saying 5'3" if this wasn't true. She would just finish her dumb spiritual point about inner size by saying 'he looks small' or something.

But she randomly picks out 5'3" as a size to laugh at because she knows, and we know, that at some point she's seen a short guy and thought 'hahaha omg he looks about 5'3"', and remembered that measurement and that feeling of mirth.