I don't think being taller or dwarf has anything to do with your self-image. People acquire liking or disliking for their height according to the evaluation by their peer-circle. Otherwise it hardly has any impact. At times, being taller or dwarfed could have its own advantages or disadvantages according to the situation we are in. But the best way to look at ourselves is to be content with ourselves. Evey being is a marvel in itself and Nature's best creation. All beings are beautiful and unique in their own way and we should discover that beauty. We should be ourselves and ignore all benchmarks set by our immediate society. Only then we can live a happy life.

BTW, I'm a couple of inches taller than you and I love myself! I sincerely hope your sis understands this. May God bless her!