Is it permissible to listen to songs with the tambourine (daf) to ensure they are free of offensive lyrics, knowing that my cousin is not religiously committed and will also listen to them in her ordinary days, and is it obligatory to warn her about this, and can the tambourine (daf) be played at a mixed-gender wedding?

Islamic law permits women to use the tambourine (duff) at weddings, provided that the recorded lyrics are reviewed to ensure they are free from prohibitions. Many jurists, including the Malikis and Hanbalis, disliked the use of the tambourine outside of weddings. Sheikh Ibn 'Uthaymeen permitted its use for a specific reason, such as the return of a traveler, and not merely for amusement. Unlawful mixing (ikhtilat) is not allowed at weddings.