Inside of the dimensional tunnel Aster noticed that the atmosphere was a bit strange, which was understandable, while Nerissa isn't a shy kind of girl but a rather calm and composed one, not to mention she felt quite comfortable around Aster due to the circumstances of their first meeting when he saved her life.
After returning to the sect, she has been constantly asked about her "relationship" with the Lord of the Twin Sword Valley, by practically all the other girls of the Black Sword faction as well as other acquittances she has on other peaks and factions.
And no one believes her when she says that they are just friends, especially since somehow those girls found out she is staying with them.