This is really sad, sorry for your loss.
Last year a breeder friend of mine and I teamed up to produce a clutch. His female lesser pin DG and my male leopard pastel het DG had an awesome clutch. 8. Perfect eggs. She went back on food and everything seemed fine. Couple months later he found her dead. It's one of those things you don't know anything is wrong until it's too late. We figured she must of ruptured something when laying not serious enough to kill her right away like yours but since we had no idea anything was wrong so it had time to get infected and eventually kill her. Sad day for sure, she was an amazing animal. After finding her, the girl that he has clean his tubs mentioned that the week before when she was cleaning her tub she noticed she passed some green stuff. She didn't know any better but we can't help thinking if only she said something sooner we could of possibly saved her. That's what makes us think it was the infection that killed her and not the actual injury, if only we could of got her on antibiotics soon enough. Never know though, she may have been too far gone anyway.
I guess you just have to accept that it's part of breeding. You hope you never have to deal with something like this but we all know there are health risks. Unfortunately if we don't see any signs soon enough, their isn't really anything that could of been done. Don't beat yourself up about it, just accept it's part of breeding and be prepared while hoping it never happens again. Once again, really sorry for your loss.