Sounds like counseling would be a good idea and please get her some help.
Use the Bible as an aid and tell her this:
1 Corinthians 7:1-12 New International Version (NIV)
Concerning Married Life
7 Now for the matters you wrote about: “It is good for a man not to have sexual relations with a woman.” 2 But since sexual immorality is occurring, each man should have sexual relations with his own wife, and each woman with her own husband. 3 The husband should fulfill his marital duty to his wife, and likewise the wife to her husband. 4 The wife does not have authority over her own body but yields it to her husband. In the same way, the husband does not have authority over his own body but yields it to his wife. 5 Do not deprive each other except perhaps by mutual consent and for a time, so that you may devote yourselves to prayer. Then come together again so that Satan will not tempt you because of your lack of self-control. 6 I say this as a concession, not as a command. 7 I wish that all of you were as I am. But each of you has your own gift from God; one has this gift, another has that.
Notice this exert from the scriptures says not to deprive each other and a wise mate will meet needs of their partner even if they are not in the mood.
This is a scripture you can share with her to show she is supposed to have these intimacies in marriage and get her some help to find out why she feels the way she does and save the marriage because kids do better with two loving parents.