She is asking for a divorce for no reason. Can he take back the mahr?

No File Exists
Check below answers in case you are looking for other related questions:
Khula’: definition and how it is done
What are the rights of the husband and what are the rights of the wife?

No File Exists
Related Answers:
Divorcing (talaaq) three times based on a belief that it is obligatory
It is not a condition of divorce that the wife should know or that she should be divorced face-to-face
Man divorcing his wife on his parents’ orders
Khula’: definition and how it is done
What are the rights of the husband and what are the rights of the wife?

Recommended answers for you:
If his wife does not agree to him being away for more than six months
Does women’s hijab have to be black?
Some du’aa’s and remedies for one who suffers from pain in his body
Why do we pray Zuhr and ‘Asr silently?
Things that make ghusl obligatory