So, update: I WAS able to tell her I was leaving. I did not come clean about the lie with her. But I did tell my mom, my sister, and my best friend, expressed how anxious/guilty I feel, and talked it through with them, which really helped a lot. I'm looking for new jobs now, and she's looking for a replacement. I'm supposed to stay until she finds someone but I'm worried; what if I find a new job and they want me to start before she finds a replacement? Ugh. As soon as things are settled, I'm making an appointment with a therapist to discuss this.