Is it just me or the raws got a diffrent style? http://lhscans.com/read-kusuriya-no-hitorigoto-neko-neko-no-koukyu-nazotoki-techou-raw-chapter-7.html
you just got the raws wrong this is the original
http://rawlh.com/manga-kusuriya-no-hitorigoto-raw.html
If im not wrong then niangniang is a way to call consorts & empress or a way to say her highness but not mother cause in the imperial harem you called your consort mother "mufei" and empress mother "muhou"
Niang Niang should be for all consorts, it's just a way to politely greet them. Fei- Should be the title. There is Empress, consort, concubines, etc. I believe there is the Royal Concubines titles too. I think there is 1 Empress and 2 Royal Concubines for the emperor to crown.
You mean huanghou,guifei & fei?
Yes. I only know them in Vietnamese