color-coding is traditionally important in henshin plots.

Well then it's curious that they specifically mentioned that the dragon was red. Maybe "Celaria" was the Red Knight.

On MangaDex, it looks like there are other non-english translations up to chapter 23 (english is still on 16).

Making a story about cooking when you don't know how to cook is certainly a bold choice.

^Had the same feeling, it was uploaded in February, don't know why it's in 'Recently Added'.

Landmine is more of a Yandere-lite than it is Tsundere.

She was just given the name 'Hanako Shimura' by that nun, right? Maybe there was an original who fit the role of villainess better.

I think this, like a lot of fiction, uses exaggeration to convey feelings that are realistic but hard to flesh out in a concise manner.

I think the word that you (and others) are looking for is "Melodramatic". While that word is sometimes used disparagingly, it's a perfectly valid form of storytelling.

The editor is a villain.

I don't remember if they mentioned Meguru's parents being divorced, or was that her mistress?

The sisters "always lived apart", so I believe the separation is assumed.

Who is this?

Same girl as here, I believe.
https://dynasty-scans.com/chapters/how_i_lose_bets_with_my_sadistic_gifted_childhood_friend_and_she_steals_all_of_my_firsts_ch2_2