Quote Originally Posted by YianKutku View Post
Lyse says "Naago", though. She mainly says "M'naago" when introducing her.

According to the Tales From The Storm, this is something Lyse decided to do on her own, and M'naago just let it be.
Yeah, just caught her calling her Naago and rushed over to this thread, got beaten to the punch. Comparing their relationship to the aforementioned relations of Y'shtola, and the fact that her close friends the other scions usually stick with the "Y", it's possible it's Lyse just being really friendly, like the anime characters that insist on referring to even just close acquaintances by their given name rather than family name, and probably got rebuffed by Y'shtola back before the game. I'd have to see her interact with other reasonably close Miqo'te to be sure, however.