Her performance matched the lowest score of Round 3 and put her at 11-under-par 205 at the Guadalajara Country Club.
Matthew will seek to parlay her advantage into her fourth career LPGA Tour win and first since the 2009 Women's British Open.
Alone in second place was Suzann Pettersen, who birdied the final hole and finished with a 1-under 71.
Tied for third one shot further back at minus-7 were defending champion I.K. Kim (70) and Anna Nordqvist (73).
A sore elbow took its toll on second-round leader Juli Inkster, who fell to a 3-over 75, dropping her to fifth place at minus-5.