Wolfick it's purely a stylistic choice!
both yin mei and yinmei work to convey the meaning across. based on my own personal preferences, if it's two character name, such as "岳梅", I would write it like Yue Mei, with Yue being the surname, and Mei being the first name character, although her name would not be Mei; it would be Yue Mei (if that makes sense lmao). if it was a three character name, such as "岳荫梅“, I would write it like Yue Yinmei since I find that this is easier to read for english speakers. Yue would be the surname, and Yinmei would be the first name, and people would call her either Yue Yinmei or Yinmei.
overall though, I would say that whether or not the translator/author picks to format her name as Yin Mei or Yinmei, they should keep the formatting the same throughout the story and the same for all the characters. (so basically, if I were to have another character named, say, "陈闻柳’, and I wrote Yinmei's name with the two first-name-characters pieced together, I would write the other character's name as Chen Wenliu because I did the same formatting for Yinmei.)
if they don't keep the formatting coherent, then that's the sign of a careless translator/author since it can confuse some readers.
hope this explanation helped. :smile: