Having the diagnosis does not change who you are. You are the same person you were before the diagnosis but now you know the things that cause issues in your life. Your therapist sounds like she really wants to help you and that is half the battle - finding someone who is supportive and can help you through the tough times.

What I have started to do (and it seems to help me) is when I am reading stuff on BPD I write down how it affects my life. So symptom 1, applies in xyz, symptom 2, does not apply etc. All the books I have been reading put everything in different order so I write both the symptom and the things that I notice in myself and the title of the book. Right now my brain is in a fog and so if I don't write it down I will forget immediately.

And don't feel nervous, we are here to be supportive.