Complete the game to unlock Bonus mode. An option for "Bonus" will appear when you select Single-Player mode at the main menu. Select it to replay levels with new parts.
Monique has two different forms. In the first form, she is in the air. During this form, just stay by a table and use radar. When she jump kicks you, use the Verretta M82 when she lands on the table. You must duck behind the table to avoid being hit by her knifes. When she jumps again, stand back up and shoot her. She will transform into her second form after you damage her to a certain point. In her second form she is on the ground. In this form you should remain behind the table to avoid being hit by her knifes. When she runs away, stand up and shoot her. Hit her when she runs towards the middle and she will charge you. Step to the side to avoid being hit. Repeat until you kill her.