Who is Ghosts - Regine from Four Major Plays and what is their importance?

The audience never quite figures out what Regine is to Mrs. Alving, but in terms of who she is as opposed to what she does, her character is very well defined. Regine is described as spirited, ambitious, independent, outspoken, and passionate, all characteristics that may have been displayed by the young Mrs. Alving before she married.