I am curious to know - if an attachment went on a holiday with friends without the BPD - would it normally trigger the BPD? I'm sure I've read posts before where this is a fairly big trigger for them.
It depends on the pwBPD. There is no one size fits all answer.
Does the pwBPD have other attachments or friends left while this attachment is gone?
Is this pwBPD more afraid of abandonment or engulfment at that moment or both?
How long is the holiday for?
Are they in the idealization phase or the devaluation?