What is Aoi referring to when she says "Comaneci"?
コマネチ is indeed Beat Takeshi's running gag from the 80s.  It is in reference Nadia Comaneci's high-leg cut leotard, hence the V-shape motion.  While the gymnast's pose is straight and beuatiful, Beat Takeshi does his motion with his legs apart, adding to the comical effect. Most people today, especially the younger crowd, might know the gag, but probably do not know the origin of the gag or the gymnast herself.  Also note that the gag is consider a bit vulgar and therefore is not common for women to go.

If you know the nature of Tesasure! Bukatsu mono, you would know that it uses a prerecorded voice track method, where the voices are first recorded, then the anime was created to fit the voices.  Most of the anime is ab lib, in other words the lines of the characters are completely up to the voice actresses, minus a few lines to get the ball rolling.  Karin Ogino, the voice of Aoi, tends to spit out whatever is on her mind without much thought.  She also likes vulgar jokes that are unbecoming of her job as an idol, and he has a tendency to repeat running gags. I doubt much thought was put into this line as well, other then perhaps because it is a bit vulgar.

Unfortunately I do not have that season's BD, so I can't check the commentary so see if it brings any new information to the table (Though the other season's commentaries weren't very "informative" either).

Comaneci (gag) reference.