I use her and do decent in this game:
https://swgoh.gg/u/teague/
I think she's very under rated. The only teams I absolutely hate fighting are Maul teams. She and Boba are both bad against them. So I struggle to beat them. Fortunately, they're slowly going away.
She's great against any pre-taunt characters. She's easily the fastest character in game if the other team starts with zero buffs. I like her against Jedi teams too, as she'll remove every buff, despite foresight.
To use her best, you need a zeta on her passive. I wouldn't bother with her lead zeta. There aren't enough serviceable Night Sisters for her to be a good lead.
Daka is the only other Night Sister worth anything. Great help in GW. Decent arena choice, but I stopped using her there in favor of better choices.