http://www.arondight.jp/imasss/callnames.htmboxes highlighted in grey are what the character calls themself
chart of what characters call each other
they changed their nickname from chi-chan to chihaya-oneechan because chihaya was uncomfortable with that nickname due to obvious reasons.
Also, -chin is somewhat of a slang for -chan but its originally used with calling babies, instead of -kun or -chan they use -chin.
ami mami have met hibiki but never talked to her, hence the reason why she doesnt have a nickname