She rolls forward into it, kills the first two intruders, and later sits high above the throng firing down.
Katia Grim uses her gun form twice at station 36. The first time is a snap reaction: a pair of juvenile Krakaren beasts slink into the chamber from one of the main railways rather than the new escape tunnel, and she rolls forward, turns into the sentinel gun, and takes out both while everyone else sets up perimeter positions. She then returns to humanoid form to stand with Carl and Imani C.
The second is sustained. As the waves thicken she goes back into gun form and towers over the defenders, choosing to sit high and fire down into the throngs alongside hundreds of other crawlers throwing fire.
A three-legged living gun emplacement rising above a crowd of defenders.
Katia's static firing form, used as both rapid response and artillery.