Put Laurel into the same situation Sara was, she would have probably turned out worse or maybe wouldn't have survived at all. Sara has a survival instinct. Sure, what she did wasn't great, but with the other alternative being getting raped and possibly killed by a bunch of barbaric pirates, you'll hurt a couple of innocents to ensure your own survival. As for the league, she owed them a life debt. We know that killing innocents wasn't easy for Sara, as it chipped away at her soul. In the end, she chose death, over re-joining the League.
Laurel to me is too emotionally unstable. She's more likely to become the next Huntress, than Canary. Look at the manhunt she led when she couldn't cope with Tommy's death. Or how she put 6 bullets into the fake brother blood. Six freaking bullets. She didn't simply rescue Oliver, she wanted to make sure the guy is dead. That was cold murder.
And then you have the occasional small scenes here and there, where Laurel quickly loses her temper. Like when Sara mentioned Oliver might not be ready to settle down. Laurel had crazy eyes.