Hi canadianmate,
considering that the topic is on the table and she is seeing some aspects of the condition it may be best if you support her seeking treatment. One way of looking at treatment for BPD is that it is really about learning valuable emotional management skills. Nothing wrong with learning . Targeted BPD treatment where the person is interested in improving has a very high success rate - and nobody deserves to suffer, she does want to live a better life.
I am afraid after all of the years of carrying this secret that I have made it worse and just don't know what to do.
Don't take responsibility here - there is no good way to deal with the dilemma BPD forces on us. A good starting point are the LESSONS at the top of the Staying Board page.

,
a0