Though this name was a literary invention, it has won fame due to British actress Vanessa Redgrave (b. 1937). However, it knew great popularity in Spain through singer Manolo Escobar's adopted daughter, born in 1978.
The name Vanessa is also widely used in the Portuguese language, both in Brazil and in Portugal (I don't know about the Portuguese-speaking African countries, but I'd assume it's an ordinary name there, too).