Overall the essay is good although it does seem a bit off topic, you can try changing a few things.
Not only did she change my world but she also affected my aspirations and dreams. I enjoy her company so much and enjoy playing a role in a child's life that I now want to work with children in whatever profession I choose. The experiences I have had at home and at a childcare I volunteer for have pushed me towards working with kids.
This, I believe, is your prompt. If you can add to it and include deeper insight on the importance of your dreams and aspirations I think the essay will come full circle.
Also, try mentioning the effects your sister had at home
after she was born (the world you come from- your family/home). I really hope this helps you.