Obviously I'd feel differently if it were my sister/wife involved, but it was an accident. The only person Chrissie wanted to hurt, was Robert.
And yes, she torched his car, and that was dangerous, and there was an explosion. But she could NEVER have predicted the helicopter crash - how on earth could she foresee that?!
She came forward straight away and owned up to it, took the blame and her punishment, and she's never tried to worm her way out of her responsibility.
No, maybe she shouldn't have torched his car, but she targeted Robert's materialism as one of few things that might hurt him.
I feel quite sorry for her, the deaths of three people (the pilot died too, yes?) on her conscience, she never meant to seriously harm anyone.