You cannot control her behavior or her actions. You can decide not to have her read your papers anymore because she doesn't give you the feedback you desire. You can decide to ask her to tell you what's good about your paper and also what she thinks could be improved, and then it's her choice to decide if she's willing to do that.
But you cannot prevent her from being "mean" and you cannot prevent her from being critical. So don't expect to. Instead, figure out what you really want from someone you give your paper to and make sure your sister is someone you think can provide it. If she is not, find someone else.
