My mother has always been abusive, and I ultimately got used to it. Nothing that she says or does to me now surprises me in the slightlest bit. I expect everything from her and nothing at the same time. You have to ponder the advantages and disadvantages of staying vs. moving out. If your mother pays the bills and cooks for you, I think it's worth the effort to put up with some nasty comments. If it's just psychological abuse, there are ways to ignore it, or make it less painful. One of them is staying at home as little as possible and engage in different activities to keep yourself busy. Try also to spend time with friends or people that don't make you feel like crap.
Authorities usually don't intervene unless there's physical violence involved. In that sense, you could try to make her hit you and then sue her. This will likely open an investigation, and you mother may be forced to follow a treatment if she's found to be mentally unstable or abusive. This an extreme situation, and in your case I'd say it's much better to leave without telling her goodbye. Once you can afford to move out, erase her telephone number and don't tell her your address, so she won't be able to find you.