This is explained in ep 9, because he saw a signal from his wife. Di Yue being in the Sect for some time probably…
Not her signal during dinner. He saw a leaf signal earlier as he was heading out of the cave, which is explained in ep9. Something they discussed before their missions.
did Liu Ying know that Xun Xu was a spy from Shu state?
Not clear yet but I can’t help thinking she does know or else why are her damsel-in-distress femme fatale charms directed at Xun Xu. Their meeting seems too coincidental. Unless love is going to turn her into a double agent?