Eren's conversation with Sara was effortless.
Eren first answered various questions Sara had which mostly revolved around how Eren and Alephee knew about her beforehand. Eren didn't have to struggle to come up with a reason. He just used Katalina as a reason they knew Sara.
Eren told Sara that Katalina always talked about her, making Sara happy and eager for her meeting Kat. The butcher then mixed facts with fiction to create an intriguing blend of conversation. This entertained Sara, made her content by getting all the answers she needed, and kept her intrigued at the same time. Eren also assured her of a safe passage to the White Raven city. She would come with him when they left the capital.