Alright well, I guess I'm wrong. No idea what the hell I'm doing wrong but I've tried different things over and over again and still get stuck in Resistance Ch. 5.
I've failed all the Ch. 4 missions I could, gone back and won them, killed 100 people to be sure Evil Lvl. 3 was the highest you could get, etc. Basically all that's left to try (unless I'm missing something obvious) is to run it back from the beginning and attempt to follow the guide again step-by-step, or see if maybe it's because I didn't level up her H-Proficiency all the way to A or something. Dunno what the hell it could be, and I'm too frustrated with it to go all the way back or grind H-Scenes (what a novel concept).
If no one figures it out by tomorrow I'll give it another shot, but I assume someone will. In the meantime I'm gonna stop cause this is frustrating me more than playing f'in Sekiro.