LW1-- Since your sister has turned the family cabin into a "pay to stay" arrangement send her a check for your planned nights.  When you get there and she asks for the supplies, smile and say you misunderstood.  Tell her you thought that SHE wanted to pick up everything and that's why she asked for money.  BTW, only do this if you have previously asked about helping to pay for the maintenance and upkeep of the place.  I "took care" of the family place for 9 years and everyone loved to show up, but they never thought of the electric bill, the property taxes, the lake improvement association, cleaning, mowing, etc etc etc.  It didn't bother me, because I enjoyed it from May to October every year and distant family members usually only came July 4th week.  Maybe this sister is different, maybe it bothers her.