Oh please!! Every saas is someone’s mother. Whether it be beta ki maa ya beti ki. Given a mother’s mamta, by that logic, beta ki maa bhi apnay beta ka ghar nahin kharaab karegi.
I know of girls’ mother who has been fitna in her daughter’s life and was so interfering her daughter got divorced. So it’s not maa ya saas ya baap ya susar - it’s about who the individual is.
And moreover, what about the couple - don’t they have the sense God gave them to 1) learn tolerance, patience and grace and 2) know how to balance relationships and be fair to everyone involved?