you are 100% right and from my experience most of the people who were with me at the doctors did not know what they had and jumped on it when someone gave them a diagnosis and a hope.
Yeah, that is a terrible idea. Borderline is not easily fixed (though it does mellow out, often completely, around 35 years of age) and trying to fix it by changing yourself to suit their needs is not going to work. Only a trained professional can do what is needed to help people with borderline manage. That's why I suggest trying to get a borderline person who you care about to seek help. They probably won't listen, but it's the best you can do.