I wouldn’t tell someone using that label, since over the years such a stigma has grown up around it. Borderline Personality Disorder also covers a tremendous range of symptoms and behavior, some more severe than others. If I were you, I would explain the issues/symptoms themselves, or that you have done DBT training, a kind of therapy that helps with negative symptoms and habits.
So many people could benefit from a round or two of DBT and it’s no longer even exclusively used for BPD. It’s also used in addiction therapy and in treating anxiety and depression.