Help for a speech for a younger sister?

You are so sweet to want to do this in a nice way for your sister. Why not just talk about 2 or 3 things that the two of you have done together that are special. Let it show what a great young lady she is becoming and also show what a fantastic big sister she has. I am sure there is one thing about her that makes her special that only you know about. You could talk about that also.