I really wish we get to see her snap. The dark gritty setting is engaging but her being so passive will get old eventually
It's called being depressed. Reminder she is based on a real person. Her actions are not for the sake of telling a fancy story, she is just trying to live her life and we are merely peering into it. In real life most people in her place don't turn into flashy anti-heroes either. In fact most are consumed by their emotions and struggle to escape the vicious cycle they're stuck in.
In real life there's often no crazy twists and turns, just events that haunt you for the rest of your life. That's what this manga is showing us, a story with no bells and whistles. It might not be jam-packed with action or drama, but neither is real life. Though I would still argue the specific events depicted here still tell a very unique and tragic story.
I'm not saying people in real life don't snap or that she won't snap, many do, but it's more complex, usually requiring a build up of a lot of factors.
Hell, you can argue her prostituting herself was in a way already a form of snapping, where she's given up on her life and just wanted to destroy herself, but it didn't work out and just made her loathe the world more.