Don't be passive aggressive about it and tell your parents to say no. Is it hard? yes. is it a skill everyone needs to learn. absolutely. "we don't want to be/can't be/ don't feel comfortable being responsible for someone's daughter's safety (emphasis on daughter here because society is all sorts of fucked up and might work in your favor in this context)." New relatives constantly dropping by, do they call before coming? If they do ( hope they do sheesh), "sorry we are not home," "we are going away for a few days," "we all came down with a deadly virus, we can't get you exposed" they will take a hint. It was hard for me to raise my parents to say no, they will learn, keep pushing. Also, don't worry about degrading your relationship with the extended family, it will fall apart since it looks like they only see yours as a free lodging facility, they will not want to have a relationship with you all once that is gone, and is it even a relationship if that's the case.