First of all please accept my apologies for the delay.
Patients suffering from BPD do have frequent mood swings, and change mood within minutes. Within a short period of time they can be argumentative, then depressed or may complaint of no feelings at all. These patients have highly unpredictable behavior and share a very unstable relationship with others.
They hates to be alone and always have this feeling in mind that the person they love may leave them any time. There are frequent complaints of feeling of emptiness and boredom. They are impulsive in nature and can involve themselves in overspending, substance abuse
, dangerous driving, and other harmful activities.
In there relationship with other person, either the other person is good or bad, there is no intermediate stage and that is why the find it very difficult to maintain relationship as it is very difficult for them to adjust.
Borderline personality disorder is associated with delicate self-cutting. Additional significant comorbid conditions include OCD, affective disorder, dissociative or depersonalization disorder, body dysmorphic disorder, and eating disorders.
After reading all this you can understand that even when you have tried so hard to maintain a good relationship with her, you found no success.
Once she starts getting benefit from this therapy, automatically you will see a change in her behavior and it will be easier for you to deal with her.
I would recommend the following book to know more about this disorder from your point of view.Understanding and Treating Borderline Personality Disorder: A Guide for Professionals and Families
Both of you may also try Couple Therapy in addition to her attending DBT.
I hope it helps.