You'll both be clearing immigration/customs at the same and only exit in Geneva, Swiss side (there is a separate exit for the French side).

There is nowhere to wait airside at the arrival level, all arriving passengers are funneled into immigration; you certainly won't be able to go wait at the CO flight's arrival gate, and v.v. If your flights arrive at similar times, I recommend the few chairs landside just outside of customs; standing in front of the immigration booth waiting for the other party could attract unwanted attention...

For a somewhat longer wait, there is a beverage outlet with a few tables immediately to the right upon exiting customs, which also happens to have view on the baggage claim area.