Grieving for the loss of her mother is a very healthy and important process for a daughter. Simply telling your fourteen-year-old to buck up and get on with life four months after her mother is gone is cruel--and it won't help... One of the biggest problems girls encounter after a mother dies or leaves the family is ungrieved loss.Third, expect your child to act like a child and your new wife to act like an adult.
Ask more from your new wife than from your daugher. Your new wife should be able to handle it (and if she can't, find that out before you marry her, because it's a warning sign). ...if your girlfriend can't be comfortable talking about and accepting your first wife as the mother of your daughter, you should end the relationship. If you don't, it could tear your family apart.