To be fair if there was a character that says Nya in this manga I would actually keep it in the translation like I did for Manabu in the Go Rush manga. Desuwa is a little more debatable because I first did it to maintain the "Ojousama" vibe Noel had in her dialogue but as I was writing it I felt it sounded a little silly so I just uploaded it hoping for the best and maybe change it later if it wasn't completely necessary. but I literally just now uploaded chapter 2 and one page had a text box dedicated to Noel saying "desuwa" and now I feel like I have to commit to the bit. I genuinely have no idea what to do about that.
When I translate I usually want to give the impression that while you're reading it in English you can tell the characters are speaking Japanese by their mannerisms or speech pattern, which can very easily be lost in translation. So an Ojousama character like Noel and an overly formal character like Cybilla are really hard to adapt.