so sorry to hear that!! I hope she's not doing too bad considering that's one hell of a gnarly looking break! Putting out positive vibes for a speedy recovery for her.
I Never had any kids myself, but I imagine you r going to beat on yourself over this, and would do so even if you were nowhere near the hill when this happened. Seems a pretty natural response for a father. I wouldnt expect anything I could say would change that!
Even so, try not to be too hard on yourself. She was doing something she enjoyed and you participated and supported her in that activity! Not a ton of parents that can/would do thay!!
Best wishes tothe both of you!