Thank you all for the responses. They are helpful. My husband has texted a couple of times over the past couple of weeks asking if she’d like to come here for the holidays, or go on a trip with us instead without any response. I’m trying to view this as her needing space. I’m telling myself perhaps it isn’t permanent. I’ve read somewhere(maybe here) that chasing someone with BPD who doesn’t want contact is like quicksand and can only make things worse.
Think of your daughter like a flame. To burn, she needs a flammable material (wood, paper, cloth, etc.) and an actual spark.
For a long time, you were her spark. But she's moved on and found something that seems to fit better. And that's okay, at least you're somewhat removed from her endless need for attention and blaming.
But like any flame, the material eventually burns out...relationships fall apart from an all too familiar pattern. Like she did with you, she moves on and needs a new spark to keep her flame burning. Maybe that's you, or your husband, or someone completely new. But there's always that need for the basic components of who she is.
For BPDs, the people they're closest to are also the people they have the most instability with. Relationships come and go, only to return again when there's nobody left. So this definitely is not for forever and you can't take it personal...this happens to absolutely everyone in her life at some point.
As soon as they become irreplaceable, that flame burns brighter and the material will inevitably burn up.