Contrition can be either perfect or imperfect. One can confess mortal sin because one is truly sorry or because he fears hell. Either way the sin is forgiven, but imperfect contrition leaves lingering attachment to the sin.
I don’t wish to be unkind in speculating about the husband, but I also think it unkind to simply dismiss the wife’s grief. Maybe she’s not simply harboring resentment for an old sin; maybe some residual attachment to his sin is the problem. I certainly think she should forgive her husband, but I’m suggesting that if this still bothers her after eight years, there may be more going on.
Some sterilized couples follow NFP guidelines and honor the woman’s fertile time with abstinence as a form of penance. Humanae Vitae warns that contraception can reduce women to being treated as sexual objects. NFP might reduce those feelings if they exist. The Church doesn’t require this, but maybe it might help, especially if he has any attachment to the continued birth control effects of his sterilization.
Beyond any guessing at his contrition, while a woman is of child bearing age she has monthly reminders that she is not carrying a baby. Maybe she desires another child. It is perfectly natural to desire marriage to be fruitful. Maybe God is tugging at her heart to encourage a reversal. The Church doesn’t require this, but I know people who have had them. Some have reversals and go on to have another child. Some couples simply pray together that God will send them a child if He desires in spite of the vasectomy.
Jesus most certainly offers forgiveness. I hope the original poster forgives her husband as well. Then together they can explore if any further measures are needed for healing.