How does the portrayal of Keisha contribute to his warning to his sister and what message does that send his sister?
Keisha is portrayed living the worst life possible, she is mentioned to be unhappy and conflicted "In her heart she hate it there, but in her mind she made it where Nothing really matters-". She has no opportunities and is forced into prostitution to make a living, "Rosa Parks never a factor when she making ends meet", where her own rights and dignity, symbolized by Rosa Parks, have to take the sideline.
Even though she's sick of prostitution and sex, seen "It became a practice, but now she's numb to it" and seeks a better life, she lacks the knowledge and opportunities to break out of the loop due to her upbringing "But she never heard of Catholic religion or sinners' redemption That sounds foolish, and you can blame it on her mother".
Eventually she is killed and raped. The meaningless of her life and eventual death is represented by a listing of events "And caught a knife inside the bladder, left her dead, raped in the street " showing the brevity of the occurrence and "left her dead" representing how her death was barely mourned.
Keisha's life represents the worst possible outcome for black women living in the ghetto. By presenting this to his sister, Kendrick aims to create a sense of fear of what could become to her, in order to steer her in the right direction.
The repetition of the chorus "Fancy girls on Long Beach Blvd Flagging down all of these flashy cars" and references to similar songs such as "Brenda's Got a Baby" aim to show that this is not a one-time occurrence.
The songs aims to make Kendrick's sister recognize the danger of entering this "loop" and hopes to highlight the ways she can avoid it at the first signs, by directing her to better things, such as religion through references to Christianity.