The photo was taken circa 1989, so what category is she ?

Honestly and with all respect to the photographer of this very nice photo - JUPITER in this early Fred. Olsen shape was not a cruise ship, but a combined passenger ro/ro ferry and a special capacity to freight fruit from the Canary Islands in wintertime (actually!) to the countries on the North Sea. Later they turned into more cruising business... especially her sister's rebuilding in Turku, Finland, 1987.

Yes.

Is she a sister to Black Prince (Ola Esmeralda)