Struggling to understand my in-laws’ reaction to repeated infidelity

Assalamu alaikum, I really need some Islamic advice to help my in-laws see things clearly. My husband’s brother’s wife ran off with another man and lived with him for around two months. This isn’t the first time-she’s been unfaithful with at least four different men during her seven-year marriage. I’m new to the family and didn’t know about her past. The whole situation got out, and everyone in the community knows, bringing a lot of disgrace to both families. Even her own parents have cut ties with her. Now she’s come back, and my father-in-law and mother-in-law have accepted her with open arms like nothing happened. All the other brothers, their wives, and my husband are completely against this. I’ve even moved out of their house because I feel like they’re downplaying how big a sin this is. Islamically, what do scholars say about repeated zina and how families should react? Are there any specific lectures from trusted scholars that address this? I’m looking for guidance from the Qur’an, hadith, and recognized scholars-maybe even personal opinions-so I can help them understand, since they hold religion in high regard. JazakAllah khair.