I just checked back to chapter 5. Chisaki's tits were originally smaller than Hibari's are now. Just how much bigger did they get in those two years or so? Just for comparison, none of the others had particularly pronounced chest growth.
And she is still behind her mother.
I'm not sure where the mother stands in the chest magnitude rankings... but I don't think she has Nonko beat yet. Probably 3rd place behind Nonko and that Master ghost whatever... with Matoko and Harumu in 4th and 5th... at a guess.