It is tough but it is teaching her the facts of life. Even in today's modern society things can still go wrong. I am sure she knows you did your best.
If there are any diaries in your area get a bull calf on the heifer to nurse her. Breed the heifer back and try again is what I would do.
I know many get rid of a heifer that loses the first calf but I always thought that was short sighted. You have a cow that is just one breeding cycle away from another calf. You start another heifer and it is more of a crap shot.
My Grand Dad always told me this when we lost one" If you did not have them you could not lose them" his meaning that if you own livestock losing some of them is "Normal".