If someone sues me and sends their request for me to waive service of summons but sends the request via certified mail to my deceased cousin's house, we have same name, and my cousins widow tells me about the mail she opened by mistake, same name remember, and I tell her to just ignore it and throw it away; is that a violation of any law?
You are allowed to throw away a request for waiver of service, so you are allowed to tell some other party to throw away the request. The rule (4) simply requires that it be addressed to the defendant and "be sent by first-class mail or other reliable means". The law also does not require you to waive service, it simply says that if you don't sign and return without good cause, you have to bear certain expenses. Your cause is not particularly good in this case.