Hello Machidiel, and welcome to bpdfamily
I am so sorry to hear that you're going through this. When things seem to be going so well and then suddenly collapse like they did, the pain and confusion can be immense.
I had a very similar situation happen when my undiagnosed BPD wife experienced a miscarriage. We had struggled for many years to get our relationship "back on track" and the reason she was pregnant in the first place was that we finally decided to start trying for a family. After the miscarriage, the BPD symptoms came back with a vengeance. It wasn't until she finally sought treatment for the symptoms (anorexia, eating disorder, suicidal ideation) that things started to improve again. They cycled back to a very low point again after the birth of our 4 year old.
I relate this story because it's important to recognize that cycles like this are very common, and it's often hard to definitively say "things are all better now." We have to recognize that each step is just that, a step. Keeping our boundaries (core values) in mind, enforcing them when needed, and generally focusing on maintaining a
Wisemind is essential. It seems like you are doing this - great job

Here's something you said in your post:
I need my time to process and heal, but I'm putting that aside for her needs.
Before you put aside your focus on yourself to attend to her needs, can you tell me more about how you were feeling? Were you learning some things about yourself? Did you discover needs and desires that were being shoved to the side while you were involved the first time?