The more you relate to her, the easier it is to be nice to her. For example : [substeps] Does she look up to you? Many younger sisters idolize their older siblings.
[header] How to be nice to your little sister [title] Put yourself in her shoes. [step] Many of us are frustrated by younger siblings, especially when they're being mean or annoying. The first step to addressing this frustration is putting yourself in her shoes.