Hi inter,

Asking to return my stuff, demanding I delete pictures of us on my Instagram and my personal favorite, she showed up to the beach in my hometown where me and my family spend our summers with with her new bf and family after I took her there last summer.
We'd have to look at it from the perspective of a pwBPD, a pwBPD feel a lot of shame. Part of BPD poor interpersonal r/s skills that is a cause for choatic r/s's. If she has a picture of the both you online, it's a reminder for her that she has failed at another r/s again, that would trigger feelings of shame.
She's missing developmental stages in life and one of those stages is r/'s. A pwBPD have empathy but when your thoughts are not focused on loved one and they're focus on your anxiety / depression symmptoms, shame, self loathing, intense feelings it's very hard to think of anything else.
I understand how something that you shared together is introduced to someone else without acknowledgment to you that it might hurt your feelings. She doesn't have healthy r/s skills, she has social impairments.
I totally get trying to over the angry feelings, angry is normal in a situation like this, you didn't have a healthy r/s with her anger can help you with detachment. I'd suggest to hold off on forgivenesss and shift the focus on giving yourself closure. I spoke about healthy r/s skills earlier and in a healthy r/s a partner will give the other partner a reason why they think that they can't continue the r/s. Your ex doesn't have the r/s skills to be able to give you closure, you can give closure to yourself. I'd also advise to forgive yourself before you forgive your pwBPD and some people they don't need to forgive.