Alicia is the younger sister to Alice. She was well known around the Arume empire for her devotion and wits. She however didn't get as much attention as Alice, and instead lived in her shadow. Once Alice died she was able to rise up and take the mantle that her sister was carrying. She's first introduced to the resistance when she went to fetch avrod's key at the same time that the resistance was.
Alicia looks very much like her sister Alice, facial features, body, etc. One could even mistake them for being the same person. The underlying thing that sets their appearance apart is that Alicia has long white hair, instead of short white hair like Alice. And she also younger in her facial features since she's the younger sister. She sports a white Arume uniform, with a sword at her side.
She is very much like her sister except for the fact that she is highly devoted and loyal to the Arume empire. Unlike her sister who may do what she does for herself and to advance her power, Alicia does it for the glory of the Arume empire.