Trixie was my least favorite character in MLP for years.  
I thought she was obnoxious and an uninteresting character.
 
Then suddenly…without provocation…she is now one of my top 6 favorites.  
Her antics and spicy personality is my FAVOURITE thing about her episodes. As such, I’ve been drawing her more.
 
In the Roseverse, she’s a traveling magician with a cast of several creatures that work for her. I haven’t come up with a name for them yet, but it’s a sort of pop-up circus. On her travels, Trixie has collected a lot of different talents for her show. Her pride and joy, however, is a new age Draconeequus named Forget-Me-Not from Ponyville.  
The little whelp was a thorn in her side during that visit but Trixie soon noticed how much Monster loved the pyrotechnics and maybe didn’t have a proper outlet for her energy. Seeing a lot of herself in the little dingus, she decides to take her in as an apprentice!
 
Poor Monster doesn’t know what to do with this crazy horse!
 

 

 

 

 

 

 

 

 
 
Edit: I know I’ll get this question so I’ll answer it now. No Monster is not really related to Discord. She’s part of a new generation of Chaos Creatures. It’s hypothesized that eventually, all creatures will become so mixed in the future that not one species will be recognizable. Creatures of the future will look more like Discord and Monster. But that’s just in the case of the Roseverse.  
Monster’s biological parents were hybrids and so she has a little bit of everything!