what she feels

Oh my God, is your friend is concentrating in making his family's life better and happier or concentrating on dating back his ex girlfriend at the moment? If she is a good ex-girlfriend, she wouldn't disturb someone else husband. Remember, your friend's wife is a woman too, and yes she is his wife. Maybe she is also contacting him just as a friend. She may have someone else but some people are just friendly. Just because she is his ex-girlfriend does not means if she ever contacted him again means she's loving him again. And also if your friend is devoted to his wife, then why worry? Unless if he is going to fall in love with this girl again then yes there's something for him to worry about