It's not that there weren't events in her childhood that led to her noticing that her clan, which treats most offenses as uproararious, treats one as monstrous, in a manner out of character. The problem is that the significance of that is not clear, not clear at all, until much later. And there are other hints and things that will be important later.
But making it so these hints are not tiresome as a standalone is not easy. She doesn't know what's going on, and it takes years before she learns. Even skipping most has pacing problems. . . .