Merry Christmas and I'm happy for you that you get to spend some time with your family. There is some obvious competition going on between your sister and you for your parent's attention. I think because you are spending the holidays living at your parent's that she feels somehow cheated during the holidays. I know that it doesn't seem like it but I think that there might be some jealousness it her harsh observations and the fact that she has brought it to everyone's attention several times is a good indication that she is doing everything she can to get under your skin. Unless your parents are totally blind, they are aware of the condition of your nails and although you don't say anything about their feelings, I can only assume that they are on board with you and your fashion style. It might be the time to ask your mom what she thinks about your nails and anything else you feel like asking. Have a safe holiday and a great New Year.