Sarah Briggs is a main character in Titanfall and appears in Titanfall 2 as well. She is also one of the four combat guides in the game. She is a devoted member of the M-COR and informs friendly Pilots when they can deploy their Titan. Sarah is usually in a field command role, providing logistics and important information to pilots on the ground, however, she sometimes embarks on special, usually covert missions.
As a child, Sarah lost several close members of her family to incidents in which the IMC displaced Frontier citizens by force. As a result, she vowed to take revenge on the IMC at every possible opportunity, refusing to rest until they have been removed from the Frontier. For most of her career, she served in Covert Operations for the Militia, before moving into the command ranks of the Militia's Marauder Corps. Her long list of successful attacks on IMC installations landed her on the IMC's High Value Target List, where she remains listed as one of the top 50 most dangerous Militia operatives still at large.
Her shirt bears the logo of the Redeye. It is likely that Sarah either served on or is related to the ship in some way.
Although it seems she can handle herself with a gun, during the events of Titanfall Sarah isn't seen acting as a Pilot - however she does come to pilot her own Titan, MOB-1316, during the events of Titanfall 2.
IMC's reward for her head is 50.000 credits, same with Barker.
According to Grunt chatter in Titanfall 1, Sarah's name isn't actually Sarah Briggs. One grunt comments he'd figure out what her name really is.