Proper and complete service in an unlawful detainer case is fundamental. Have you considered hiring a private process server rather than using the sheriff's office? You should also consider consulting with a local attorney to help you with this service and your case.
Under California law, the right to deposits in a joint account may be resticted to the amount contributed to the account, meaning that one cannot take out more than they put in. This arrangement is, of course, subject to modification by the joint account holders. The answer may be different under Tennesse law. You should consult with an attorney to get help and guidance in how to respond to your family.
It appears from your question that your grandmother's attorney is also the executor of her will. There may or may not give rise to a conflict of interest. As you have a very serious question and one that cannot be fully answered in this on-line forum, I recommend that you get a second option from an attorney who specializes in estate planning and Medicare coverage issues.