Lillian Mattencourt is the richest woman in the world.
Born as the heiress to a wealthy father, Lillian Mattencourt made her own fortune in developing and selling perfume and make-up products.
Presumably having learned from her father of the existence of the "billionaires club" Majestic-12, Mattencourt requested to join them after her father died. However, Mattencourt was constantly turned down, purely because of the fact that she was a woman; even the fact that her father has been a member didn't work in her favour, as several members would regularly taunt her with sexual innuendos.
At some point, through her contacts in the French government, Mattencourt learned of M-12's plan to initiate a new Cold War. After her latest attempt to convince Randolph Loch to allow her membership ended with her stalking away after Loch had said he would consider if she performed oral on him, the scorned Mattencourt decided to ruin their plans (the fact that her make-up empire would suffer during war-time was only a secondary reason for her).
Learning that one of the targets on a bounty list of people who could stop them, Shane Schofield, had a reputation for succeeding against all odds, Mattencourt realised that the Marine should be kept alive to do the tasks M-12 wanted him eliminated for. To this end, she hired the bounty hunters Aloysius Knight and Rufus by promising to pay them US$130.2 million, the equivalent of seven heads in M-12's bounty hunt.
When Knight caught up to Schofield and informed him that he was being paid to keep him alive, he refused to tell the Marine who his employer was.
A few weeks after M-12's plans were foiled, and as all of their members were being quietly assassinated by the U.S. government, Mattencourt met with Knight and Rufus in Majorca, Spain, to finalise their payment. During the meeting, Knight enquired her reasons for thwarting M-12's plans, having believed it was due to the likelihood that women would be less inclined to purchase cosmetics during such a Cold War. However, Mattencourt corrected his assumption by stating her primary reason was to get revenge for the constant spurning and taunts M-12 had put her through.
Ending their meeting, Mattencourt assured the bounty hunters that their payment for protecting Schofield would be paid by night time. However, as soon as she started her car, it exploded, having been rigged by Demon Larkham as revenge for Knight stealing some of the heads IG-88 had collected during the hunt. With Mattencourt having died before she could pay them, Demon told Knight that he considered the matter settled.