I can understand you not wanting to burn your bridges, but you could always put your move down to a 'clash of personalities' with your manager, rather than the truth that she's about as much use as a chocolate teapot. That, Add a couple of thousand on to what your new job is offering moneywise, and a switch to another department for you or the teapot, and tell them you might consider it, because sometimes, it's better the devil you know than the devil you don't. If you decide to take the new job or not, Good luck!!