What does “a body gets stuffed in the closet” mean?

"A body gets stuffed in the closet" is neither idiomatic nor common. The meaning is not completely clear to me. Just reading along unsuspectingly, I'd have supposed it to be a mangled version of the more-common "skeleton in the closet", a collocation used to suggest hidden secrets, a dark past. But looking at a book reference from ngrams gives me the impression that "stuffed in the closet" is a recently-developed set phrase referring to psychological events repressed instead of dealt with.

Regarding professional advisors on name changing based on the number of strokes of Japanese characters in one's name and date of birth, I am not aware of any such persons in the USA. Maybe in Canada?

Edit: As I note in a comment, the article gives me the impression the author means something like "my former me is buried and gone, now the new me is here"; in other words, she is trying to emphasize the scale of change she experienced.

'whenever someone changes her name, a body gets stuffed in the closet. When I think back to my old self, I think of an entirely different person, ...'

That sets it out clearly there.

When you change your name, it is the end of a certain personality. The new name makes you think like an altogether new person, a new personality, a new character in the society and so on.

So you kind of stuff the old you into the closet and start a new existence.

The practice of drawing hidden meaning from numbers is called numerology, and in the West numerology usually uses the number of letters in a word or name. Very few people take it seriously though, it's rarely if ever used to actually choose a name (only to make predictions on an existing name), and I would think very few people could make a profession of it.

Such a person (as well as a Japanese 姓名鑑定士) would be called a name numerologist.

In regard to "name doctors" I have never heard of anything similar in Western countries. Here in New Zealand there are laws that apply some restrictions to legal names such as maximum length, no religious references, cannot use numbers or punctuation. However within that framework people are free to choose any name they like for children (and frequently do). I think it's fair to say that most people in Western countries do not put the same amount of significance or importance on names as people in eastern and Asian countries.