It's gonna depend on why she has compared you two.. What makes it a negative? It is very likely you are a little bit like your sister... She is your sister after all. Try not to take too much notice of it, parents say this kind of stuff all the time. Unless you have loads of siblings or your mom is a teacher or something, what other kids is she going to compare you to? Most likely she hasn't had experience of dealing with many other kids, so your sister is all she's got to go by
