ANSWER:

If she was truly sinning and having an affair or flirting with men, she is an evil woman and tarnishing their son’s name and reputation and must be reprimanded for such a heinous behavior and not be protected and defended in such a way. 

But if this was something of the past and she stoped this, they have no right in bringing this up now and she and her husband should sort such things in between them without outside interference

QUESTION: My in laws spy on my daughter fb found her sinning & call her to say she’s bad muslim. My daughter said to not judge & us parents know everything. My in laws mad at daughter & husband. My husband respectfully told parents doesn’t have right to attack &parent our daughter regardless of sin. My question is what rights do my in laws have over raising my kids and criticizing?