I call her Crys, which is what the Japanese call her, its short for Crystal (which they also use in the manga Pokémon Adventures..where she takes Lyra's place and hates her outfit!).
https://bulbapedia.bulbagarden.net/wiki/Crystal_(Adventures)
I don't want to call her Kris. Usually I just call her Crystal. I never understood why they called her Kris in Crystal when the name 'Crystal' fits in the name entry..I guess its probably a left over from the Japanese version calling her 'Crys' (
クリス) since Crystal (
クリスタル) was too long for their name entry. Since
クリス is pronounced the same as 'Kris', they probably didn't catch the reference to the version name when translating it and thus made it Kris instead of Crystal, which would have matched the other games which had Red, Blue, Yellow, Gold, and Silver by having the version also being a name option.
I honestly kinda hope that Pokémon Masters retcons her name back to Crystal.