Blimey, if you change the details in the OP to the boss being a "him" not a her, I'd wonder if you were at my old place.
It's a long story and it still upsets me now - it was the job I'd always wanted, and I really enjoyed it. I was the favourite when I got there, and was for a long time.
Anyway, the boss - who treated me like his cleverest friend and confidante for ages - eventually turned on me and made life intolerable. I went from loving my job to crying all the way home every night because he'd been such a massive arsehole over nothing, and I couldn't do right for doing wrong. It was as though he'd built me up to enjoy breaking me down again. All my self-confidence withered and died, I was second guessing my own decisions and then he'd berate me for being spineless.
It wasn't until I was forced to take up a second role alongside my own, that I could barely keep up with already, that I cracked. I handed my notice in and things became a bit like what Yellowfish describes in their fantasy company. I brazened it out until the last day, when he turned up grumpy and late to my leaving drinks, stood up in his coat for the standard "Wish you well for the future" and instead said he wasn't signing my card on principle, had not contributed to my leaving gift, and said I was very disappointing. In front of the team I managed.
Absolute dick to the end, I sobbed all the way home for the loss of what I'd hoped would've been my last ever job, the loss of my confidence, and for ever having been taken in by that utter wanker in the first place.
But there is a happy ending. About 2 years later he contacted me on LinkedIn to ask if I would be interested in a new role (it was PERFECT for me, exactly what I wanted to do). I said yes I would, and who would it be reporting to? He said, "Me".
So I got the opportunity to say "You? Ok, in that case no thanks."