A person with bipolar has different situational triggers. They aren't trigger by a person or event. They usually have something that physiologically effect them.
Example- mania- can be seasonal or affected by lack of sleep, coffee, drugs or alcohol, stress.
Also, borderline is a personality disorder. Personality disorders respond as well to meds. Bipolar is a disease and does respond to meds.
That does not happen with a borderline. I have learned there is a big difference. They can co-exist.

I am bipolar 1.