Frederica has long pale gold hair and green eyes. She is a little taller than Subaru, has a muscular build, and a mouth with sharp fangs. She is mentioned to look like a carnivorous hunter locking onto its prey when she narrows her eyes. According to Subaru, Frederica would be a beautiful woman if she covered her mouth.
Unlike her younger brother Garfiel, Frederica uses her father's surname Baumann. She is a kind person although she can be strict at times, especially to Petra who just started working as a maid. She also cares deeply about Garfiel and sends him letters every once in a while. As children, she used to spar with him and often sent him flying, completely ignoring the seven year difference between them. She lacks the courage to wear cute outfits because she thinks it doesn´t fit her frame.
Frederica was born around 22 years ago to a father who was a half beastman and a Human mother, Reala Thompson, and was born a quarter beast human. Eventually, after wandering around, Frederica, along with Reala and Garfiel, were picked up by Roswaal and given a home at the Sanctuary. Reala left her children at the Sanctuary to bring back her missing husband. Frederica lived at the Sanctuary until she was 12 years old when she became a maid, working for both Roswaal and the Miload Family. She quit her job at the Roswaal Mansion a couple of months earlier but came back as Ram couldn't handle the mansion by herself following Rem's disappearance.
Beastification: Thanks to her quarter demi-human lineage from her father's side, Frederica can either fully or partially transform into a large leopard beast. This puts her on the same level as Rem with her demon horn.
- According to the author, Frederica's birthday is December 6.
- According to the author, Frederica is scheduled to be featured in arc 7 and her main arc is arc 11.
- Frederica's blood is of a rare kind, and according to Clind there can be dangers associated with it.
- A bit of divergence from WN, Frederica in the LN can partly or fully Beastify like Garfiel. Naturally, this replaced the Cestus weapon she used in the WN, however did not change her fighting style otherwise.
- The dress that Subaru used when he dressed as a woman belongs to Frederica.
- Her hobby is to collect dolls and putting cute clothes on them.
- Frederica needs to gnaw on knives to wear her teeth down because they keep growing.