Ariella left using her space-element rune, leaving no trace behind.
She promised to meet Eren and Agatha often in the city of White Raven. She had to if she wanted to ensure the deal got properly executed.
Eren was still sitting at the rickety table. He had various thoughts running through his mind at the time. He needed to calm them before leaving the place.
Ariella had agreed to pull some strings and see what she could do about arranging a meeting between Eren and Ottoman. There were no promises. But Ariella had to put in genuine efforts because she had struck a deal with Eren. One needs to take care of their business partners after all. Especially if the business partner was someone like Eren.