Am I the A

I ( F 22) recently got diagnosed with ADHD. My older sister ( F 25 ) claimed it obviously isn't true because im in my early 20s it would have been caught earlier. I tried to point out that if your not looking your not going to find anything. My older sister has tried to be the center of attention my whole life so I was kinda in the shadows a bit. My mom (F 45) will even agree that she focused a little more on my older sister then me. So my older sister said well then she will get tested for autism. But in the back of my head im wondering if she only wants to get tested for autism because she wants to be back in the spotlight. If she has a more "serious" disability maybe she would get more attention. She was evaluated many times growing up and they never found autism. Nor anything remotely similar to autism. She met all of her mile stones at an early age. Except for reading because my family has a long line of learning disabilities. Am I in the wrong for thinking this way?