Imagine a situation where the client in a case is an elderly lady who is forgetful and completely inexperienced in the law and she relies on her son to help her with a legal case. The son engages an attorney and pays for the attorney, but the old lady is technically the "client" since she is the party to the case.
The lawyer then ignores the son, and communicates only with the old lady and tries to get her to agree to things or only reports his actions to the old lady. The apparent attitude of the lawyer is that since the lady is the client, he need only answer to her and in matters of judgement, all that matters is his (the lawyer's judgment), not that of the son, even though it is the son paying the legal fees and the lady relies completely on her son for legal and business matters.
What is the right procedure for this situation? How should it be handled from legal and diplomatic standpoints?