Bless the OTP
 
Darn Discord messed up Celly’s beautiful sunset and just as she teleported to him, in hopes of yelling at him, he brings out a bouquet of cake. It takes Celly a moment to process everything. She held a cold glare until..  
Snort
 
I totally picture these dweebs as a stereotypical tsuandere relationship with Celly hating him for a long while before coming to grips with the fact that she’s not hated him all this time, she’s hated that she loves him. Once they make it official, Discord is thrown off at how goofy Celesttia is around him. For all the grief she gives him for his chaos, he’d never expect her to prompt him to mess with his magic later on. She’s got a dirty sense of humor and loves discords chaotic pranks, as long as no pony is hurt of course.  
On the other hoof, Celly could read Discord like a book but was ultimately shocked he ended up with her. It was a constant battle in her head to force down her feeling, “He destroyed old Equestira, he is evil.. so why can’t I stop thinking of him”. In the end, she let it go, and forgave discord, realizing banishment in stone for 1000 years was plenty punishment. She found his charming ways rather endearing and when Discord tried, he could be quite the romantic.
 
Fun side note: Fluttershy is Discords best friend and he constantly talks to her if he and Celestia are having a rough spot. He even consulted her when trying to woo the Sun goddess and would share his anxiety with her. Their relationship is incredibly strong and they always look out for each other. Fluttershy couldn’t be prouder that her friend Discord found the love of his life and Discord begrudgingly admitted Flutter’s husband was a fine choice.