Dorothy M.Nicholls;91;of Fayette City (Lowber) R.D.;died Tuesday;March 30;1999;in the Mon Valley Hospital;after a very short illness.  She was born Sept.19;1907;in North Belle Vernon;a daughter of the late Jesse and Mattie Pascoe Spang.  Mrs.Nicholls was Methodist by faith.  Survivors include her husband;William S.Nicholls;two daughters;Dorene Little of Perryopolis R.D.;and Joan Vogel;of the state of Maryland;three sons;Arther Gaskill of the state of Ohio;Donald Gaskill of Belle Vernon;and Robert Gaskill of the state of South Carolina;12 grandchildren;19 great-grandchildren;and one great-great-grandchild.  Friends will be received Wednesday from 7 to 9 p.m.and Thursday from 2 to 4 and 7 to 9 p.m.in the Eley/McCrory Funeral Home Inc.;334 Main St.;Fayette City;and Friday until 11 a.m.;the hour of services;with the Rev.James R.Myers officiating.  Interment will be in the Belle Vernon Cemetery.  The Eley/McCrory Funeral Home Inc.is in charge of arrangements.