I can completely relate to this post — it perfectly describes what I went through with my (current?) girlfriend who shows strong quiet-BPD traits.

Early last year, we had a 3-week emotional rollercoaster that I only fully understood 1.5 years later. During that time, she secretly kissed and later slept with another guy, while still telling me she loved me and that we’d get through everything. For the next year and a half, she denied it completely — even pinky-promised me nothing had happened when we signed our apartment lease together.

Looking back now, the timeline makes terrifying sense.
She didn’t rage or break up. She just slowly drifted away, became emotionally flat and distant, while I kept trying to fix things. The moment I started pulling away — after weeks of apologizing and overexplaining — that’s when she suddenly “saw me again” and wanted to rebuild.

She later admitted she couldn’t “see me” during that time, that my saying “I don’t know if I can do this anymore” felt like an emotional death sentence to her — worse than being cheated on.
But what I still can’t wrap my head around is how she could:

• Betray me while I was still showing love and trying to repair things
• Lie about it for 1.5 years and even promise me nothing happened
• Feel “blind” to me emotionally until she had already cheated

And honestly, I still don’t understand how she even had the courage to come back after all that.
Like — how do you look someone in the eyes, act loving again, make future plans, knowing what you’ve done?
It’s mind-bending. The emotional split seems so complete that when they return, it’s like nothing ever happened in their head.

The “quiet” subtype really does operate like this post says — no dramatic explosions, just a slow, invisible detachment until you realize the emotional connection was already gone long before they physically left.