Sibling rivalry is a normal thing that happens almost in all the houses where there are siblings. It usually begins to increase when the younger child is crawling and getting into the older one’s stuff.
Although this rivalry is a normal circumstance, as parents we must try it doesn’t increase and increase. The first step is prevention.
While it is important for the elder sibling to learn to share, it is reasonable for her to have some toys she doesn’t let her sister use. You can help her choose which toys she can keep for herself and play with on her own.
Once a conflict arises, tell the older sister you understand why she’s upset and help her empathize with her sister.
If she feels that you understand her and that she can understand her sister, it’s easier to find solutions with her. If your elder daughter is involved in solving the problem, she will want to carry it out.
But, remember, that NOT sharing and play by themselves it’s important, too. They must have the opportunity to play without a little sister messing things or without an elder sister leading the game.