I find it funny that one of my players guessed that Mulan was a Servant before I even finished making the game, and they actually didn't meet the Servant until halfway through the war. No one actually learned her real identity until the very end, and just about everyone freaked out because someone had guessed her.
Rider's Mistress was Haruka Tosaka, unknown younger sister of Marta Lualdi and the Tosaka family's heir. Haruka ended up being a fairly well-developed character by the end of the war, but being an NPC's Servant and having so many players made it hard to focus on Mulan. She was very obedient to Haruka, and it was when they were trying to escape from battle that Archer shot at them and caused the fall of a skyscraper which would mark the first casualties of the Seventh Holy Grail War.
For all of her frailties and lesser abilities compared to some of the other Servants, Mulan managed to survive until the end of the war with her Mistress, although she was severely injured in her final fight against Archer.
Fate/Zero, Fate/stay night, Fate/hollow ataraxia, and all contained therein are copyrighted to Kinoko Nasu and his company, Type-Moon.
Fate/last guardian, Fate/forever wishes, and Mulan Hua the Rider-class Servant are copyrighted to me.