Sentence:  The daughter of the family, Katie, was older than I, an accomplished seamstress who helped me sew my first garment, a pull-over apron, and showed me how to <WSD>scallop</WSD> the neckline of a linen blouse. 
Meaning of the word marked with <WSD> tags:  To create or form an edge in the shape of a crescent or multiple crescents.