Help I’m drawing a blank! Looking for a word that describes a person as having a small build and also fits into the sentence “she was a _______ of a woman”
Oh yes, I believe you are looking for "wisp" as in, "a wisp of a girl", or in the case of your sentence, woman.
Merriam-Webster's definition here.
“she was a dainty woman”
- Delicately beautiful or charming and usually small: