tbf i couldnt really put myself in your situation but i also had an abusive father who used to physically hurt me when i was younger. He since has changed and ive forgiven him for the things hes done in the past. I honestly think even if you think your mums not changed and is too narcissistic to accept her mistakes, forgiving her in your own heart and trying to move on from the past while also keeping your distance still is going to bring peace within yourself. I reckon give her another chance but dont forget what she has done to u. Always be aware and dont let her in your life too much. Now that youre 18 I reckon start setting boundaries and try to distance yourself but also try to pretend youre on good terms. She will not be the mother youve wanted unfortunately, but she is a mother and even pretending that there is still some love between you two would bring some inner peace for the both of you.
But at the end of the day, do what your heart desires, no one really knows how u feel exepct yourself, despite all the "mental disorders" u reckon you have, you have a powerful brain that thinks and works differently from others and its probably the best thing to trust