Sleep Disorder. She becomes scared!

Dear Sir, My wife is a nursing mother for a 2 month old child, she doesn't have any professional or personal issues in her life. We are a happy family, she is living her perfect life. Right now shes under her maternity leave and feeding child, I have my mom and her mom to assist us in our daily household helps. From past one week she couldnt able to sleep, inspite of her body being tired, she herself say that I am feeling tired and i m yawning a lot, but I am unable to sleep. I have asked her what are you thinking when u lie on bed, any disturbing thoughts or nightmares, she said nothing much (here I would like to say, one of her school mate lost her husband a week ago, she was bit upset about it, i counseled her stating as it is beyond our control we cant do much about it, so for couple days that particular thought was keeping her busy) later that thought is evaded as per her, but shes saying she developed a phobia that she may not sleep in night, as the night falls she becomes scared