Hello and welcome, Shadowflame

It's smart to reach out for support, feedback, and thoughts, as you're considering one of the biggest decisions a person can make in life: who to choose to partner with. Many here will understand the feelings of having a deep bond with a person who also struggles with BPD.
In order to understand your situation a little better, I'm curious about a few things:
Now she’s physically and digitally absent – not working, not posting. But she’s still leaving symbolic signs that she hasn’t let go of me. I feel called to respect her process and stay passive – allowing her to meet me cleanly if she returns. But it’s difficult.
Tell me some more about how you're noticing the symbolic signs from her -- I think I'm understanding that you two are not physically around each other? Has she left the community? Are others telling you about what she's doing?
How do I best respond to her absence without reinforcing her self-destructive patterns?
Am I tracking with you, that you're concerned that if you don't respond to her (somehow) while she's absent, that she'll repeat self-punishing behaviors? Or is that not quite what you're asking?
How should I act if she returns, possibly with a new “mask”?
My first thought is that you'll know more if/when that comes to pass. Not super helpful -- but in a sense, helpful, because it highlights that sometimes we spin ourselves out about the what-ifs, before anything comes to pass. Sometimes the things we wonder about do happen, and sometimes they don't. Can we trust our future selves to have the strength and wisdom to know how to field that encounter, if it happens?
Alternatively, or in parallel -- are you in any kind of counseling or therapy for ourselves?
As counterintuitive as it sounds, BPD relationships can become more livable when we focus on us, not the person with BPD. Our article on
The Do's and Don'ts in a BPD relationship touches on how important it is to maintain our own emotional health, regardless of what our pwBPD is or isn't doing.
Building your own resources, and getting good neutral third-party professional feedback on your thought processes, can only help you as you ponder how to navigate a reconnection

Is it even responsible or realistic to have a relationship with your twin flame when she exhibits trauma-linked or BPD-type behavior?
Persons who struggle with BPD often have all three of the following:
-high emotional sensitivity,
-high emotional reactivity, and
-long return to emotional baseline.
Anyone can have any of those (I tend to be emotionally sensitive with a long return to baseline); however, a pwBPD will likely have all three, plus low skills, high shame, and a tendency to blame/externalize due to those factors.
This makes it difficult for a pwBPD who isn't getting professional help, to maintain a healthy intimate relationship -- the intimate partner may be on the receiving end of low-skills attempts by the pwBPD to manage her overwhelming shame and emotions, and those attempts (blaming, raging, self harm, infidelity... the list goes on) are unfortunately really damaging to relationships.
This isn't about who is right or who is wrong, who is healthy or who is unhealthy -- just describing the fact that when a pwBPD isn't getting meaningful help, then almost by definition, her (or his) closest relationships will take damage.
People stay in those relationships for all kinds of reasons (commitment, marriage, children, finances, etc), and so what we focus on here on the "Bettering" board is how to work on your own stuff to make the relationship more livable for you.
I’m very interested in your perspectives – especially from those who’ve experienced deep soul bonds and/or intense relationships with someone with BPD traits. I’m not trying to “save” her – but I also don’t want to make things worse by being present. At the same time, I feel like she is “mine” – and that creates an internal conflict I’m still trying to work through.
How long have you known her?