Mathelier, a junior at Binghamton University, scored in the 47th and 56th minutes and the Lady Stallions (12-3-0) advanced to the Eastern Conference final this weekend against defending champion Boston Renegades (13-0-1) or the Ottawa Fury (11-2-1). Boston and Ottawa meet Thursday night in Framingham, Mass.
Princeton junior Esmeralda Negron scored in the 16th minute and assisted Mathelier's first goal. William Patterson University hall-of-famer Kathleen Sinram, a Lady Stallions assistant coach, also tallied for the New Jersey.
Long Island (9-6-0) outshot the Lady Stallions, 18-9, but former Green Mountain College goalkeeper Sarah Allen made 13 saves for New Jersey.
Columbia University career goalscoring record-holder Tosh Forde and Duquesne University senior Lauren Bracco scored first-half goals for the Lady Riders.
Charlotte plays host to Northern Virginia and Northern Kentucky visits Chicago in Central Conference divisional finals on Thursday.
New Jersey Lady Stallions 4 (Negron 16, Mathelier 47, 56, Sinram 77) Long Island 2 (Forde 28, Bracco 45)
Boston Renegades (13-0-1) vs. Ottawa Fury (11-2-1) at Bowditch Stadium (Framingham, Mass.), 7:30 p.m.
Charlotte Lady Eagles (9-3-0) vs. Northern Virginia Majestics (5-7-0) at E.E. Waddell High School (Charlotte, N.C.), 7:30 p.m.
Chicago Cobras (10-1-1) vs. Northern Kentucky TC Stars (5-5-2) at Mooseheart Memorial Stadium (Mooseheart, Ill.), 8 p.m.
Vancouver Whitecaps Women (10-1-1) vs. Seattle Sounders Women (8-3-1) at Swangard Stadium (Burnaby, British Columbia), 10 p.m.
New Jersey Lady Stallions (12-3-0) vs. Boston or Ottawa.
Charlotte-Northern Virginia winner vs. Chicago-Northern Kentucky winner
Aug. 8-10 at Landstown High School, Virginia Beach, Va.
Hampton Roads Piranhas (12-0-0) vs. opponent TBA
Opponent TBA vs. Opponent TBA