.. i feel like my heart wants her and her attention, but my brain knows what I have been through the past month and I'm afraid it'll happen again.
And it "will", unless you decide to completely dis-engage all personal interaction. We end-up punishing ourselves because in spite of being at the "breakup stage", our feelings still run deep; we are still deeply wounded, raw and vulnerable. They call/text/etc and we engage again, except nothing really changes. Insanity for sure.
It took me more than a month to finally accept that by staying-engaged, I was only hurting myself. My BPDxw was literally "pulling my strings"; emotionally playing with me. At some point I had to ask myself if I genuinely had any "self respect" left.
In your case, having to be around her because you work together is a tough one. I was able to bury myself in work to help me get through each-day; avoiding any personal interaction. In your case you are going to have to separate the personal side from the professional side, and considering you still have feelings, it is going to be tough.
Ending a relationship with a BPD partner is hard enough. Having to see this person everyday at work makes it even harder. Leaving a job because it's the only way to get away from them is not really an answer either, if you continue to stay engaged at a personal level (no I'm not suggesting you should leave your job, but do re-consider coworker relationships in any future relationship and do consider the problems they can bring).
You may want to get some counseling, as many of us had our own issues that kept us trying in a relationship that was totally dysfunctional. Counseling helped open-my-eyes regarding how I was continuing to hurt only myself, even during the break-up phase. You are vulnerable and she knows it. She'll take all the favors you give her and then she'll move on.
Not sure any of this helps with your situation. I can say that once you are out of this relationship (she is just another person at work; someone you pass on the street), you will realize how deeply enmeshed you were. It's sinister and hard to heal from, but with time, distance and working-on-yourself, you will.
All the best
