I'm pleased to hear, for a start, that you have a good enough relationship with your daughter that she was able to come and talk with you about this ( at least, i hope that is what happened !) Continue to discuss this together and work out a joint strategy for discussing this with dad. Maybe she will know of a good local gay / lesbian organization which can advise more specifically on this, as their members will have experience of similar situations. Although he may feel a mixture of emotions, including anger, disappointment, etc, he will probably settle down before long and recognize that this is only one aspect of the daughter he has always had good reason to love, and still does.