Hidden in the parking garage of the Atrium at Chestnut Hill is this whiz with the sewing machine. Yelena, mother of Tatiana (as in Bridals by Tatiana), is the seamstress with the mostest. No alteration is too difficult or too hurried for her. We tested Yelena with a pricey Vera Wang gown that had to be refitted in 24 hours; the job included ripping seams, restructuring a bodice, and hemming a fitted-waist A-line skirt. The result: Not a thread out of place.