Hello Kano ,
Anxiety is something I am all too familiar with. I felt the same with my ex ... .too anxious and concerned that bringing up my concerns and feelings would cause her to dysregulate.
Giving her space is good when she needs it, but you also can't continue to avoid the issues that are causing a divide in your relationship.
What makes you think she suffers from BPD? Given she is in DBT (which is great) I assume she has been professionally diagnosed?
Have you had a chance to check out these articles?
Is it Borderline Personality Disorder?DSM Definition: Borderline Personality DisorderGood communication is critical in a relationship, especially when dealing with a borderline. To that end leaning how to effectively communicate without triggering her can take you far.
Here is a good place to start learning about effective communication tools.
Communication Skills - ValidationI also encourage you to check out the workshops, specifically with respect to threads on communication.
WorkshopsFeel free to ask any questions and share more of your story. It helps clarify things when you write it all out.