Whiplash triggers on splash , any splash skill/flamethrower in Boss on multiple sub bosses and she procs on the splashed damage (not the initial damage).
Overkill triggers on critical hit, multiply/amplify the single hit.
She might have triggered and you didn't notice it. There is no extra message or popup if she triggers in bosses. The only way to tell is if you get more points than usual.
Thats right. she didnt splash at all. i used more than 5k worth of staminas. non of the splash proc. How do i know? non for the Critical hit dmg are more than 4 times.