She simply wants you to run after her, fight to win her back! From my experience this is very easy to guess! Remember they are emotionally children and don’t know how to approach in a mature way!
Good luck if you want her back and let us know of the outcome!
Exactly. Seems to me she's very much testing you if you'd be available and willing to date someone other than her. Most BPD's find it very hard to put themselves into a vulnerable position like asking if you'd want to come back to them: the chance of being rejected is way too high and painful so they use covert means.
In a way I might even advise you not to tell her from this point on that you're only interested in her. Yes, it's the truth. And it probably feels good for her to hear that. But often that little assurance that you're 'available' is enough to satisfy them. Because this way you provide her with the ultimate comfortzone: she has not lost you, but she also does not need to commit.
Do not give her the assurement that you're available. Just keep it to 'I do not want to discuss my dating life', or 'My dating life is my own'. It's a signal to her that just by standing idly by and not taking a risk/broaching her fear of commitment she will eventually lose you. Up to her if she values you enough to take that risk.
It is a bit of a foul game, playing her mechanisms like that. But at the same time it's not you who invented the rules of this game. You're challenging her to confront her non-productive fears and if you're sure about your intentions to be a good partner this could be very teaching and helpful for her.
You should also consider whether you'd actually like to continue this dance and whether it's not too much effort.