On Wed, 20 Jan 1999, Matt Johnston wrote:

And, if you reveal a problem, it makes you sound more human if you also
offer a solution, like, say the proper spelling/pronunciation.

I suppose that's a fair enough request.  "Xian Pu" is a mistranslation
deliberately introduced by Richard Lawson, who was aware that it was a
mistranslation and probably didn't expect that he was creating an everlasting
fanfic cliche.  The kanji for Shampoo's name are shown in the manga.  I can't
confirm this myself since I don't have a Chinese dictionary, but supposedly
they are pronounced "Shan Pu".  The meaning of the kanji, from Theresa
Martin's guide, are "coral" and "uncut jade".