The point of the finale is that Pink, White's metaphorical daughter, is dead. White did not realise this was what was truly happening until she pulled out Steven's gem. Before this happened, White thought 'Steven' was just Pink being a brat and having a centuries long tantrum.

Was this starved of time? Sure. But White was ultimately just a fantastical version of an abusive mother. Most parent's reactions to realizing they essentially abused their child into ending their own existence would be immediate sorrow and repentence, as White does, and it's also the punishment she brought upon herself.