Sorry, I don't know where else to write this...
Seriously, who ever said that about Kinana?
Volume 21 Bonus, Guild Cards?
All it says is that she was a snake, not Cobra's snake.
Also, I believe that card with Kinana is actually fake, since I don't remember ever seeing it in manga, and I checked it again.
I'm guessing this is the typical for some Wiki editors - to make up some things.