Calonice is Lysistrata's neighbor, and just like Lysistrata, Calonice is respectable middle-class housewife. Think of her as the Ethel Mertz to Lysistrata's Lucy Ricardo. At the beginning of the play, Lysistrata hasn't yet told Calonice what the mystery meeting is all about… Calonice is on time because she is just that friendly and eager to help out:
Calonice: "Well, Lysistrata dear, what exactly is this business you're calling us women together for? What's the deal? Is it a big one?"
Lysistrata: "It's big."
Calonice: "Not juicy as well?"
Lysistrata: "Oh yes, it's big and juicy."
Calonice: "Then how come we're not all here?"
Lysistrata: "That's not what I meant! If it were, we'd all have shown up quickly enough. No, it's something I've been thinking hard about, tossing it around night after sleepless night."
Calonice: "After all that tossing it must be limp by now." (21-28)
We can tell, from her constant double-entendre-ing, that Calonice is as much of a sex fiend as the rest of Athens. But she's also just a chummy neighbor.
We learn more about Calonice's apolitical and pleasure-seeking temperament when Lysistrata warns about how all of Greece might end up being destroyed if the Peloponnesian War continues. Calonice doesn't catch Lysistrata's drift and thinks it would be completely okay if Athens' enemies the Boeotians and Peloponnesians got wiped out—just so long as there were still some delicious Boeotian eels to eat:
Lysistrata: "Yes, our country's future depends on us: whether the Peloponnesians become extinct—"
Calonice: "Well, that would be all right with me!"
Lysistrata: "… and all the Boeotians are annihilated—"
Calonice: "Not all of them, please—do spare the eels!" (29-37)
That said, as soon as Lysistrata reveals that her plan is all about putting an end to the war, Calonice enthusiastically agrees to join her.
Once the other women show up for the meeting, Calonice relapses back slightly into her earlier small-mindedness. Once again, she starts making fun of people based on where they come from—including people from the 'burbs of Athens. When a group of women show up from the suburb named "Stinkton" (which: really? That's what you named your suburban hamlet? What's wrong with Pleasantville?), Calonice complains about how those women smell.
She may care more about eels than human lives, and might be a little to eager to make fun of women from Stinkton (bahaha—Stinkton), but she's a loyal companion, and ends up helping Lysistrata's cause no little and quite some.