Pam had been denied access to the gardens during her stay in Arkham, and it took a very stupid guard she used pheromones on to get her access to it. There was a lot to hate about the place, however, like Jonathan, she appreciated that they at least cared for the gardens. It was possibly why she hadn't made it the first place she wanted to attack.
"Somewhere," she answered vaguely, "I suppose my home, though that would require you to stay indoors until I find you a suitable living situation." It wasn't that she trusted Jonathan to know where she lived, but more like she didn't think him a threat to expose where she was. Thus far, he'd be nearly amiable, despite their initial impression upon meeting at the Gotham prom.
Near the back of the gardens was the exit for the staff. Most of the people who had access to the gardeners were accompanied by nurses and not allowed near this area. But there it was. An easy exit. A vine nearby stretched out and opened the door for them and Pam smiled, touching the original plant with a gentle stroke, "I'll come visit you soon, darling. Don't worry." The vine twisted around Pam's hand briefly before letting go. And she made a hasty exit out the door.