Versailles no Bara, Paros no Ken Recommendations
Erminia and Oscar, from the Rose of Versailles, both wish to be males. There is no yuri relationship in the Rose of Versailles, but Rosalie, similar to Fiona, have yuri feelings for Oscar.
Erminia and Oscar are similar characters and they both have a similar dynamic with their respective childhood friends. Both mangas are stories about members of the aristocracy wanting follow their own path in life but not being able to due to their duties.