Not exactly sure what you mean by "what" she was...obviously a Princess. Future Queen of England!
Because Prince Charles was - and still is - the Prince of Wales when she married him. Her name was never Princess Diana. He correct title was Diana, Princess of Wales.
Because she married Charles Prince of Wales Hope this helps
Diana became HRH Princess of Wales when she married Prince Charles on July 29th, 1981. After the divorce in 1996 she had to give up the HRH (Her Royal Highness) and became Diana, Princess of Wales. She was never officially called Princess Diana.
Charles, Prince of Wales
Because she married Prince Charles of Wales.
Because she married Prince Charles of Wales.
Lady Diana Spencer, later the Princess of Wales, married Queen Elizabeth II's eldest son Charles, Prince of Wales on Wednesday 29th July 1981.
Princess Diana became a princess after she married prince Charles. The prince of Wales and heir to the throne of England.
Princess Diana Frances Spencer was married to Charles Phillip Arthur George.
Princess of Wales Diana Spencer was married to Prince Charles of England in 1988. The two of them were divorced in 1996.
Lady Diana Francis Spencer married His Royal Highness The Prince Charles, eldest son of Queen Elizabeth II of The United Kingdom of Great Britain and Northern Ireland. It was, of course, only after the marriage, that she became Princess Diana.
Diana, Princess of Wales