Margaret L.Dudick;55;of 115 Reed Ave.;Belle Vernon;died Saturday;June 25;1988;at 12:55 a.m.in Mon Valley Hosptial.  She was born Nov.19;1932;in Coraopolis;a daughter of the late John Williams and Eva Stemmler Mayer of Charleroi;who survives.  Mrs.Dudick was a member of the Clavary Bible Church of North Charleroi.  She had lived in Belle Vernon since 1981;moving into the borough from Charleroi.  She retired from Bell Telephone Company in 1981;having worked in the Charleroi office for 30 years.  In addition to her mother;she is survived by her husband;Paul Dudick;one brother;Joseph E.Williams of Severn;Md.;and two nephews and one niece.  Friends will be received Saturday from 7 to 9 p.m.and Sunday from 2 to 4 and 7 to 9 p.m.in the Ferguson Funeral Home;Inc.;700 Broad Ave.;Belle Vernon.  Services will be held from the funeral home on Monday;June 27;at 11 a.m.;with Pastor James R.Worstell of the Calvary Bible Church of North Charleroi officiating.  Burial will be in Belle Vernon Cemetery.  Arrangements are being handled by the Ferguson Funeral Home.