Depressed Nine Yr Old

I just had a long talk with her so she could calm down a bit and take her mind off it but my niece gave me this letter today. It broke my heart and it’s not the first time she’s written something like this and shown her mom. She said she feels like it will never go away. I also suffer from depression so it was difficult to tell her it will get better when I still haven’t figured it out. She asked about therapy and wondered why no one talked about feeling that way at her age. I explained all I could about what I know and how I’ve dealt w it too. Her parents are divorcing and she is wondering about her bio dad and just had a big move up to where I live by my mom (her gma). A lot of changes so I understand where’s it coming from. She said she has always felt this way since she can remember. She’s only nine and always says she doesn’t want to grow up ): I wish I could take that pain from her so she doesn’t have to so quickly. I watch them almost every day so I feel more responsible than her mom who hasn’t been around much lately. How do I handle this..