Welcome to BPDFamily, happy to meet you, sorry you're here...
It's a complicated situation, but the first thing to realise I suspect is that if you think she may prefer to live on the streets than return home...then we're going to have to set aside hopes of bringing her back into the house. Even if you brought her back, her...perceived trauma, disdain or hatred for the house is likely to cause her to relapse right back out in the same way she left last time...but twice as bad. At least, that's my experience.
Of course, it may be that the idea of the good job offer is overwhelming to her; many BPDs have a severe haltlose, they don't want to make plans more than a few months ahead. In that vein, it might be worth considering whether you're able to convince her to take this great job opportunity "but just do it ironically, for a few months, you know to get the monthly income, the benefits, maybe meet a really handsome accountant/astrophysicist/doctor/secretary/dentist" or something like that...and then cross your fingers and hope she decides to stay. It's not impossible for a BPD to stay in a field for years, I've definitely seen it - in part their "living one day at a time" means they don't really process how long they've been at the job...so even though they told themselves at hiring it was just for three months...three years later they're still giggling that they're going to quit in a few months, etc.
The good news is on the horizon though, the vast majority of pwBPDs will improve with age; they'll still have BPD but they'll be much better able to manage it - I think usually you'll see the improvements by 25 even if they don't have a job/spouse/calling in life...I'm not sure there's a great explanation of it, personality disorders are obviously still a field little-understood in many ways.
