I added some changes, and I have a small story about her.
As you see, my head canon towards Celestia, like Luna, she can read your thoughts without you telling, which it brought her troubles.
When Tia was 100 years old and became the ruler of the Equestria, being young and inexperienced, she didn't really know how to run her world, she worked quite hard for her people. Exhausting, eh? Not easy to running a world.
One day, she took a walk among her people, surprised to find that not everyone of them were satisfied with her work, some even didn't want Tia to rule the Equestria. She couldn't stand either, that's what you got when you try hard but not satisfied by everyone, she didn't kill them. Instead, she ran away, she ran away from her people, her country, her own world.
But don't worry, she came back in the end, now Celestia is over 2000 years old, mature than she used to be.
I add white flower petals to her crown, shows and necklace, emm, so far so good. By the way, Tia and Luna are ancient Equine horse, which they are different from normal Equine, Tia is mixture with lion, unicorn, pegasus and dragon, Luna is mixed with Seraphim, unicorn, pegasus and dragon. Tia represents Grace and Mercy, Luna represents Justice and Nemesis. I will write more head canon for them in the future.
No, Luna will leave with Celestia, at that time, Luna didn’t become Nightmare Moon. After Celestia ran away, Daybreaker took over the kingdom, you know what consequences if Daybreaker rules the world. By the way, Daybreaker design can be seen in my gallery, though I only drew headshot.
Now Twilight had to experience the same fate when she became the new ruler of Equestria. Even more so since Celestia ruled for so many centuries that their history, veneration and culture made her a goddess of the ponies. Poor Twilight had incredible huge horseshoes to fill.
Pretty sure things became harmonious after a couple of years if not ten. Who said that she didn't attempted to connect with the former deities for having news and asking for some advice? Only G5 will only tell us more, if there will be any.