While the intend of letting her live is probably to psychologically torture her it is pretty risky. Chances are that she will be able to shake of the experience after a couple of years of therapy and will get happy with another man.
In this case he has sacrificed his and another man's life to steal a couple years from her.
If he would have wanted to be as cruel as possible to her he should have at least give her some injuries that she would carry to the end of her live which forces her to remember him. Eg. dump a magazine in her leg or arm so the won't be able to use it anymore ever.






