Take naps and listen to nice music.
If you have a smartphone, bring Angry Birds or something. You can play that stuff for hours, yo.
If your sister pesters you, ignore her. If she is relentless, tell your parents. If they don't scold her, just counter her annoyances calmly. (for instance, she says "LALALALLA" repeatedly, put your music on, or if she punches you, grab her hand and push it back without hurting her)
She'll give up eventually.
