Yeah, apparently she was getting too involved in the world of Ayla. That and there were a lot of new archaeological finds she went to inspect personally.
She's one of the few people who got to explore the actual location of the Ninth Caves. She also walked around the entire area before she started writing, to get a better idea of the terrain. I assume doing all that research took a while
But in all, 12 years was waay too long. Apparently, she's already started bk 6, and has the plans for 7. There's some wild (:lol:) speculation that we should see the next one in less than 12yrs!