Because her mom knew that her dad would take everything from them the second he found out her mom had a baby girl not a baby boy.
K. I thought it was something along those lines. But they're pretty much doing that now anyways. Or, the stepdad would probably try to "sell her off" through a forced marriage. She needs to divorce his a$$.
Well there was another reason her mom hid her real gender but you find out a lot later in the story and I don't want to spoil it for you! Also her mom can't divorce her father yet because she is fighting to keep her daughter as heir to the family business. It's complicated but she has absolutely no love for him at this point. Unfortunately now that Spade Z has lived so long as a boy it would be difficult to suddenly announce she was a girl.
Kyaaah!!! It's NEVER enough!!! ε=ε=(ノ≧∇≦)ノ
I wanna read more so bad, that I'm thinking about starting over from the beginning!!!ヾ(☆▽☆)
But, I thought his/her home assistant KNEW she was actually a girl. Just no one else knew. I wonder why they're hiding the fact that she's a girl.