So, the most irrefutable advice has already been given, so I'll just state that once again: theray for both you, and her.

With that being said though, I also want to add something I haven't seen anybody else being up... Kind of an outlook that may be helpful.

I think that what probably makes this feeling of resentment worse is how personal it feels to you. Her actions had a profound effect on your life, and when you are personally effected by somebodies actions it hurts a lot deeper.

However, remove emotions for just a moment. Can we agree that there was no malice in her actions? It was a mistake? Ignorance. She was incredibly ignorant, and didn't think about the consequences of her actions.

Now, let's say there was a 15 year old boy at the dock with his younger brother. His younger brother was a poor swimmer, and he was asked by his parents to keep and eye on him and make sure he is safe. At one point the older brother gets distracted by his phone for 60 seconds as he is sending a text. Unfortunately, under horrible circumstances, his brother falls off the dock while he isn't paying attention and drowns. This was the older brothers fault, if he had have been paying attention, his brother would still be here and his parents would still have their son. He was asked to look after him, and his ignorance of turning a blind eye is the reason his brother is gone.

My question to you is, do you think this is unforgivable? Is this mistake truly beyond redemption?

I think most people would answer no.

Is that hypothetical truly that much different than your daughter's mistake? I feel like if I was in your shoes, sitting with this for a while might help. I'm not sure how easy it will truly be for you to seperate the emotional betrayal you feel and look at things truly as they are, but I hope you find success. For both you and your daughter's mental torment.