You have to start the heist quest in act 2, do not attack the catgirls, and return in act 3. When you return to complete the heist, you have to complete one of a couple different skill checks (potency or charm I think). If you pass, Inej will knock out Heloise and you get the option to take Heloise (the inquisitrix) or two treasure.
To get Sabetha and Inej, you must take Heloise and tell them where your lair is. Telling them lures them in as Sabetha tries to steal your treasure. This is where the traps come in and you capture the Catgirls.