Nami bug (how to steal a kill with your E)

So I have been playing a bit of Nami the past couple days, and my little adc partner was taking the enemy out. It was getting a little bit too close of a fight so I cast my E onto my team mate, it provided just enough damage to finish off the enemy in one last hit, but I am the one who got the kill. I was able to reproduce this again the very next game. I don't mind getting that kill at all, but it should have gone to the adc since I was not even in auto-attack range, and my heal was still on cooldown so it was not that either.