What should I do about my wife who always asks for divorce without reason, and who seems stable when she is with her family but instigates problems when she is with me, especially since I have a daughter with her?

You are not obligated to divorce your wife merely because she asks. Her request for divorce without harm or a legitimate religious reason is religiously forbidden, and she must repent for it. As stated in the Hadith: "Any woman who asks her husband for divorce without any harm (to her) will be deprived of the scent of Paradise." If you wish to divorce her, weigh the benefits against the harms, and do not divorce her until after attempting to reconcile with her and understanding the reasons for her request for divorce.