Okay Ginny Malfoy, there are a few things that went through my mind.
First, maybe the boss is scared of you. She (or he?) sees how hard you work and thinks that you might take her job.
Second is a suggestion for you. You should ignore what you boss says. If you feel that you're doing your best, don't push yourself too hard. If you get results, forget what she says and be satisfied with yourself.