[She has zero idea how to explain this. But she tries.]

Well. Maybe not "worlds." It's... it's very confusing, and I don't quite understand it. But I think people are making different decisions in our worlds. We come from Thedas, but in her Thedas one thing happened, but in mine something else happened. [A thoughtful pause as she considers this. Then she barrels forward.] I didn't realize things were different. Leliana knew about Anders in my Kirkwall, but this Leliana isn't the same as my Leliana. They're different and know different things.

Like... like if you kept kittens in boxes that were the same on the outside but with different decorations inside.