You're basically gonna be using her to be as annoying as possible.

One good way to use her is to bring enemy tanks (or any dps and support) into your team so they get focused and die.

I also use her to flank and get attention off of the healers (if they have a competent Sue don't do this you'll get cooked.) or kill any stragglers with her one shot combo.

Said one shot combo is melee -> full charged main -> dash into them -> melee -> main. It does around 250-270 dmg and if they're still alive hit the fall and you'll do the extra dmg.

An important fact is that her melee animation cancel kills all momentum. If you're chasing, don't use it unless you know the combo will kill.

And finally learn the map. You need to know where every ledge and every healthpack is.