I remember watching a scene from an anime that showed a girl with orange/brown hair dead inside of the cockpit of some sort of mecha. I vaguely remember her or another character that died being asked to be shot if her mecha was immobilized and a monster was about to kill her. One character cannot bring themself to shoot her and later sees the orange hair girl dead in the cockpit surrounded by some sort of monster, which either had tentacles or was a writhing mass from afar. The mechs had 4 limbs and had a lot of gray. The show itself was digital and I don't really remember when I saw it, but definitely from 2014-2019. I didn't actually watch the entire thing, just that scene. The background looked a bit like the image (a screenshot of aldnoah.zero) here but with all the lights off and the structure being more decrepit.