No, I don't use it for appearance, though I do use it for weight: She was so light that he could pick her up with one hand.
Afterthought: Sorry, I should have said that I don't use it for physical appearance with the meaning "thin" or "slim": I might use it for physical appearance as the opposite of "dark" eg she was very light-skinned.
Light when used to describe a person usually in the literary world refers to character i.e. frivolous, insincere, inconsistent e.g. Browning´s poem "A Light Woman" or Henry James' short story "The Light Man" which described people who did not take things very seriously.
But today we do as Loob and PP say, use it for light in weight.
Can you give us the full sentence?