Punctuation is used to structure and organize the writings. It helps in making more sense and clarity in the sentence.
The sentence which is written correctly is Mrs. Ellis, a petite woman, wore the finest dresses from Paris.
This sentence is correct because it uses the punctuation mark comma appropriately to make logical groupings. Also, it helps in segregating one list from another. Hence, the above sentence comma is used to separate a series of phrases.
In addition, the above phrase is appositive. An appositive is a phrase or word that points to the same thing as another noun in a sentence. It helps in providing additional information about the noun. For instance- Mrs. Ellis, a petite woman. Hence, it is separated with commas to remove appositive and without changing the meaning of the sentence.