Ok, So I just punch her one day? And then what? Instructions unclear.
Option 1: She apologizes to you for doing whatever it is she thinks warranted getting hit. You know she's not just casing your joint or setting you up as a mark. Please note, you don't necessarily have to hit her. It's the spirit of physical violence. Sexual violence is too close to home and too detrimental, so don't rape her for fuck sake! Just either smack her or threaten to smack her. Make sure it's because of something you can at least start to justify to a drug whore. And make sure you don't let her run off, because the important thing is if she doesn't get instantly threatening back, you need to apologize and show her how much you really care and that you're not like those other assholes who don't see how wrong they were an apologize.
Option 2: You hit her, she flips out threatening you. At this point, you know she's not desperate or scared, and went into your 'relationship' with a plan, most likely to rip you off, and if you're hitting her she's willing to escalate that plan from petty theft to something more.
Of course, the smarter thing is to not let a fucking junkie know where you live or what you have there worth stealing. Also, make them think it's more than just about sex. Too much of a working relationship and she'll just extend the business to consciously scheming to rip you off. Make her think/feel that if she rips you off, not only will she be betraying your kindness and love, but also that she'll get hit again; that is if you did the right thing and hit her to gauge her loyalty. Also puts in her mind that if you hit her on fairly good terms, imagine what you'll do if she robs you.
In summary, she's a junkie and she's gonna rip you off at some point anyhow if you were dumb enough to take her to your place. Only thing to do now is mitigate damage by hitting her.