I dunno. The worst thing that happens to Abby is being captured by those bastards at the end(can't remember the name of their group). But that didn't really fee like it had anything to do with her revenge. I think, even if Ellie were totally out of the picture, Abby still would've ended up helping Lev. With the all out war going on, she still would've en ostracized and had no choice but to go looking for the fireflies anyway. Really, if anything, killing Joel saved her life in the end. If she hadn't taken her vengeance, Ellie never would have been there to cut her down from that poll. It just feels like everything that happened to her was just a result of the messed up world they live in. Revenge didn't require much sacrifice on her part outside of maybe damaging her relationship with Owen and his girl.
Err... Abby lost her father when she was a teenager, and then lost all of her friends by Ellie's hand (after she made the mistake of sparing Ellie's life).
Ellie lost only two friends in this process (Yes, I know Joel was like a father to her and all that, but he was not her actual father).