Shasta stared into (Bree's) great eyes and his own grew almost as big with astonishment.
"However did you learn to talk?" he asked.
"When I heard the language of men uttered by my mare," continued Aravis, "I said to myself, the fear of death has disordered my reason and subjected me to delusions...And now my wonder was so great that I forgot about killing myself and about Ahoshta and said, 'O my mare, how have you learned to speak like one of the daughters of men?'"
"Another thing," said Aravis. "You must tell your people to treat those two horses very respectfully. That's part of the secret. They're really talking horses from Narnia."
"Fancy!" said Lasaraleen. "How exciting! And oh, darling, have you seen the barbarian queen from Narnia? She's staying in Tashbaan at present. They say Prince Rabadash is madly in love with her. There have been the most wonderful parties and hunts and things all this last fortnight."
Both Shasta and Aravis are shocked by the existence of talking beasts and need to have Narnia's fabulous populace explained to them. Lasaraleen barely reacts and immediately segues back to her favorite topics. This could be because she's more worldly than either of them and has heard more about Narnia. But I like to think C. S. Lewis did it to show Lasaraleen's shallowness.