With an estimated 550 mothers present - all 70 years of age or older - a Summit Hill woman was joyfully reunited with her sister from Czechoslovakia, after a separation of 45 years, as a highlight of R. D. "Dick" Edwards' 27th annual Mother's Day fete at the Lehighton Armory. Mrs. Stefanie Michalik, 65, of Velke Kostalny, Czechoslovakia, accompanied by her niece, Mrs. Anna Ostrozlik of Smolence, was flown here from behind the Iron Curtain for the tearful reunion with Mrs. Pauline Marek, West Hazard Street.