If your mom has a personality disorder such as borderline personality disorder, they are very difficult to treat (Dialectical Behavioural Therapy is the only treatment I know of that has been shown to help), but educating yourself about it can help you cope.
I recommend everyone who has a loved one with an mental illness or other serious mental health problem they don't recognize or want to get treatment for read "I'm not sick! I don't need help!" by Xavier Amador, which has some practical strategies for loved ones.
You might also want to read up on borderline personality disorder, to see if any of the information and strategies there for family applies to you. Without an actual diagnosis, we don't know what's going on, but some of the information might be close enough to be helpful to you. Here is some evidence based information on BPD: http://www.heretohelp.bc.ca/newsletter/ ... y-disorder
And here is a story from a person with BPD in recovery: http://www.heretohelp.bc.ca/visions/bor ... borderline