The term is "prima donna," NOT "pre-Madonna." This term has been around far longer than Madonna, and not to mention, why would a commonly used term be defined by Madonna's pre-stardom-consumed life?
Here's the wikipedia article to explain it (wikipedia is reliable, STFU):
An excerpt from the article:
"Originally used in opera or Commedia dell'arte companies, 'prima donna' is Italian for 'first lady'. The term was used to designate the leading female singer in the opera company, the person to whom the prime roles would be given. The prima donna was normally, but not necessarily, a soprano. The corresponding term for the male lead (almost always a tenor) is 'primo uomo.'
"Legendarily, these 'prima donnas' (prime donne in Italian) were often regarded as egotistical, unreasonable, and irritable, with a rather high opinion of themselves not shared by others. Although whether they are truly more vain or more hot-tempered than other singers (or than any other people in the opera houses) is not substantiated, the term often describes a vain, obnoxious and temperamental person who, although irritating, cannot be done without."