This is the state of Thunder Burst in the My Older Pony story (story link: My Older Pony - Saving the Capitaine Thunder Burst)  
https://www.deviantart.com/thebenalpha/art/My-Older-Pony-Saving-the-Capitaine-Thunder-Burst-850401825
 
As you can see, it is not in very good condition. She has drunk too much, and she is no longer able to assist Spitfire at the Wonderbolts.  
After the death of this sister, she is not really the same.
 
Here’s an old drawing that shows Thunder’s condition when she lost that sister: Sisterless  
https://www.deviantart.com/thebenalpha/art/Sisterless-816608617
 
If you want to see more of the project, here is the folder: https://www.deviantart.com/thebenalpha/gallery/74451249/project
 
Even if you find it hard to believe it, it pains me to have written this to my characters.