Your original text is mostly clear, but it could benefit from some minor rephrasing for improved clarity and flow. Here’s a revised version:
"Sometimes, I wish I had an older sister I could confide in without fear of judgment—someone who could be my world. Instead, God made me an older sister. If you have one, please cherish her; it’s not easy to be the older sibling."
Feel free to adjust any part according to your personal style!