This is one of the most common scenarios Certified POP Family Coaches see and can help you solve.  If you want to try yourself first, enroll a friend to “mediate” or have a talk with your sister by yourself and let her know how you feel and what you believe you need from her.  But it sounds like you and she have some problems that predate this one and, frankly,  will only get worse as your parents age.  You are likely to become resentful and lose out on the support that your sister could bring you practically and emotionally.  If talking by yourselves doesn’t help, we suggest you pursue getting a Certified POP Family Coach for a session or two to help you unbundle this knotty problem.