She is first seen in Chapter 3, Decadence, in the same room as the Producer. After the Producer is killed by Jacket, she tells him to "finish what he started" and that she "knew it [her life] would end like this". Instead of killing her, Jacket takes her to his apartment, giving her a new chance. Other characters refer to her as Jacket's girlfriend, implying that they become romantically involved. As the game progresses, Jacket's flat becomes tidier and she starts to sleep in the same room as Jacket in Chapter 8.
After she is killed by Richter in Deadline, Jacket who is (probably) both sad and infuriated, decides to avenge her death by killing off anyone that had anything to do with her murder.
It is speculated that Don Juan in the Masked Figure scenes is actually Hooker, as she is the only one that cares about Jacket and knows he is a killer. This is supported by the box art for the game. Also, the Don Juan mask is unlocked by getting a high score in Decadence, the mission she first appears in.
Hooker in DecadenceEdit
Dialogue in 'Decadence'Edit
H: Yeah... Just get it over with...
H: I knew it would end like this *cough*
[Jacket carries her to the car.]
[If Jacket tries to leave without her]
H: Hey asshole, you can't just *cough* leave me here. I got nowhere to go.
H: Why don't you finish what you started?
ENDGAME SPOILERS FOLLOW:Edit
She is later killed by Richter, who is another masked assassin killing for the clandestine janitors. After Jacket gets the information he needs out of him. It is optional to kill him by choking him to death.