What do I tell her? Go no contact forever? Be direct and honest why I broke up, keep it short and simple? Motivate her and be extra nice or does it make it harder?

I read everything about BPD now, but of course that does not solve all my limits while interacting within a month: 1. My avoidant style triggers her 2. Me sobbing and telling her all is good and so on will not help her move on I guess. 3. Me wanting to help her wont work I guess (Co-dependent issues).

Have you ever had an amicable break up? What helped you? We search for flats but might live together a while.

CONTEXT:

I broke up because I was at mental and physical limits and couldnt help myself otherwise. Didnt recover from a fight and talking about it made things worse. Its pretty tragic and we have very strong feelings for each other

I went to another country for a few months, but we now have to have contact again and bring everything to closure. I think neither of us wants to hurt the other person anymore. But the emotions will make it hard. Its definitely not a normal breakup, I have never felt like my life would never be good again.

Me:
Also sensitive person with ADD &amp; Depression which flared up again due to all. I kind of f'ed up my college plus job. I am definitely not over her and cry every day. I know we wont be part of each others life anymore and wished it all went different. I had no profound information on BPD, only went to counseling on how to handle her abandonment issues. I did not understand the rest.

Her: 
Has a new job and just moved the city last year with new SC. No support from family (toxic people), keeps her problems secret from friends. She works on her anxiety, but has (accountability problems due to shame I guess?). She is texting very diplomatically and seeks closure, wants to know why I broke up (which I do not get because we talked a lot about our problems and that I am at my limits)