She is obviously working for a Sergie type character, he decides the rates not her.
If she had the brains to go Indie she could easily charge £120 an hour and double her earnings without fucking 15 punters day in day out. 
If "Sergei" actually exists, he is an idiot because Nicole could charge more and still get a steady stream of punters through the door.
It's not a question of having the brans to go indie, it is getting a decent place to work from. No landlord is going to rent their place to an 18 year old girl fresh off the easyjey from Warsaw, with no references and no credit score so she is
dependent on a "sergei" landlord from that point of view at least.
Hopefully this episode with the cops will convince her to find a better and more discreet place.