Romancing the Rogue by Erica Ridley

She lives in a castle that is filled with ghosts and she has become expert at bookkeeping and billiards.  Her guardian has forgotten she's even around.  She stays away from the servants.  And she enjoys her life.  Unfortunately, her guardian dies...

The author and Net Galley let me read this book for review (thank you).  It will be published March 21st.

Her new guardian wants her out of the castle and married by the end of the month.  She's not even dating but he doesn't care.  He tells she can choose or he will do it for her.

When the will is being read, an old love of hers comes to hear it.  He and his grandmother shamed her at a public event and she refuses to have anything to do with him.  He refuses to take no for an answer.  He wants to resume his friendship.  When she beats him badly at billiards, she intrigues him.  It's not appropriate for a woman to be good at math or billiards but she does it so well and he loves it.  Soon he realizes he loves her.  The fact that she's a no one doesn't matter to him.  But society won't accept it that well.  And she's not reciprocating his love yet.  But he doesn't give up.

A matter of compromise makes it work and it ends happily ever after.  I'm glad.  I like happy endings.