Nico's line is a (modified) reference to the live drama short "レッスン開始!" from the BD/DVD "μ's First LoveLive!" where Maki is having Hanayo do vocal exercises and makes her say "Maki-chan is amazing" and such things.
Basically, she's saying "Maki-chan is cute, Maki-chan is amazing, Maki-chan is..." but in between she's saying Japanese syllables with the same starting consonant sound as the adjective she just said.
If anyone can figure out how to translate that, you deserve some kind of medal.
H-Huh!? How does that work? I don't get it!!Since I'm a dog, you have to be a cat♪As expected of my Honoka. So cute. Horosho!Maki-chan's so cute, ka ki ku ke ko. Maki-chan's amazing, sa shi su se so. Maki-chan...
The iterations of "ka ki ku ke ko", "sa shi su se so", and so on are iterations of the Japanese alphabet.