This is a missable achievement in Chapter 2. There are actually a few opportunities to do this in this chapter, but it may be better to do sooner than later.
After the bartender makes the Volcanic Berserker alcholic drink for Lilli, Harvey will stop her from drinking it if she tries. Hynotize Harvey and enter the alternate world. There will be a cup of coffee in place of the Volcanic Berserker drink on the bar's counter. Drinking the coffee will let Lilli return to the real world. Repeat this sequence until the achievement pops. It will take awhile, so just be patient.
If you missed the chance to get this achievement the first time, the next opportunity will come at the police station. When Harvey prevents you from leaving, hypnotize him again. In the alternate world, there is another cup of coffee that appears on the counter of the police station that you can drink from. Back in the real world, try to leave again to have Harvey re-appear...then rinse and repeat.