write up a nice letter explaining how much you appreciate the opportunities that she has given you, and the trust that she has placed in you, but you have decided that it is best for you to make a change in your professional life. If you want to elaborate on the "things that have happened", do so in a professional manner (e.g. not "Joe's a jerk" but rather "the current working environment has had a negative effect on me")
Give her the letter in person, saying something like "I regret to tell you that for personal reasons, I am resigning with 2 weeks notice. My last day will be X. I've written a letter explaining the situation. I want to thank you for everything.
don't burn your bridge. Give appropriate notice.
she'll probably try to talk you out of it, and maybe offer you things to make you stay. if you're 100% certain you don't want to, go in with the mindset that there's nothing she can say to change your mind. People are often 'talked into' staying somewhere with promises that things will change, but they rarely do and if you're unhappy now, chances are you'll still be unhappy if you decide to stay.