You could take a bold step and ask her POLITELY what exactly you are doing wrong and what you need to do right. It could be that there's something you aren't doing well, but you are so blinded to what you currently feel about your boss. It could be that, yes, you are her project, but she wants you to harden so that you can succeed when you take over. Succession planning. Or maybe you've been telling everyone it was your idea to set up the department and the rumor has reached her and she wants to remind you who's boss. All these are maybes. But sorry for what you going through.
Luck is when Preparation meets Opportunity. ~ Lucius Annaeus Seneca