Well, without having read 'akuyaku reijo no tsuihou go light novel', it could potentially revolve around the journey of the female villain character after being banished. It might show how she copes with the new situation, whether she tries to change her 'villain' status, or if she embarks on a new adventure in the new environment she's been exiled to.
I'm not sure specifically as I haven't read it. But generally, 'light novel' often contains various elements such as adventure, fantasy, and character relationships. It might be about the story of a certain 'akuyaku reijo' (villainess) and her exile ('tsuihou').