u/Anjif

It's really good at shutting down assassins (and colette). Before there wasn't much use case but nowadays people force mortis edgar and whatever else on any map and this has more viability, not to mention it was actually buffed a couple months back. Also, it can take a Kit off of someone. Pair the stun with a Finx super and it's just a free 2 seconds to setup and annihilate your enemies.
2 more tidbits: Apparently the stun can stack in a way with the Meeple stun? In the video
The "stun" does NOT actually cancel animations, it just pauses them. So if you have a Bull/Colette charging, it will continue charging after the stun. This however still allows you time to escape and setup while you know where they will end up.

Since she got buffed and has come back into the meta, I figured I'd share some tidbits about her. Maybe some will find it helpful?
Main Point: Her super's trajectory curves according to your movement. If you move side to side? It curves that way. If you move forwards/backwards it will increase/decrease her super range. This is useful to help you land more roots.
Secondary Points: You can move backwards during her super to hit a sweet spot and get 2 ticks of super damage. Also, she's one of a few brawlers that can activate the hypercharge after the super is already sent out and still get the hyper effect.
As for the ice gadget, you can maximize its effectiveness by anticipating enemy movements and baiting them into your morningstars, making them slide and then hitting them with a root immediately.