force your way past the guard in the area where the mall meets the slums in the city, then later enter the slums through that same route, then go through dons place and do grunt work for him, then go back to cassie and talk with her, you will see a new dialog option click that then sleep, when you wake up she will be gone, go through fawns route and ask her about the don, then go to arlene the police officer, talk to her, then go to the slums and go to where they all sleep, you will need alot of money on you, pay them then go to sleep then track down the guy somewhere in the slums go back to the sleeping area pay them again, and sleep then go back to arlene and talk to her, then go back to dons hideout and at the entrance go on the tile that lets you recue cassie (SAVE FREQUENTLY THROUGHOUT EVERYTHING) then once you beat all that you should have gained cassies trust, i explained it because the wiki got rid of most of the details making it harder to figure out, in case they change that and the details are added back heres the wiki Cassie - Lust Doll Plus Wiki (miraheze.org)