(I beg to differ. I've read a lot of books where they'll do anything for the only friend they've ever had in life. They were more than brothers or sisters. I think that would especially be the case for over 20 years.)
Gaynor felt a slight urge to laugh. This was so oxymoronic. A trained killer breaking down crying. But she didn't. She couldn't help but imagine the whole thing happening. She thought for a moment. "I won't kill you if you won't kill me."
"No," Gaynor said, shaking her head. "You see, you could see it as one of us spared the other's life, so in return, the other doesn't kill the other. But there is still a debt owed to both of us. You do not punish the sword for the sins of the wielder. So I will go and kill them. You've worked for him for how long? And they still haven't returned your friend to you? So, we kill them, and then I get my revenge, and you get your friend."