Hi Bak,
It's possible that she's going through something, but (this is going to be hard) it's not your responsibility to take care of her or make sure she's ok. I know it's a lot easier to say that than to accept - I'm struggling with that myself.
I also work in the same building as my BPD ex and it takes a lot not to check on him. When I broke up with him, I asked all of his friends to make sure he was okay and show him that he has a strong support system that isn't me. He immediately started seeing a specialist and has become sober, and so it makes things a lot easier for me to know that he is doing the right things to take care of himself, but I know if something happened it would be very easy for me to get sucked in and feel responsible for taking care of him. Really, even asking his friends to help him is going beyond what I'm "supposed" to be doing, but for me it helps to ease my mind without keeping him dependent on me at all.
As much as you can, though, try to remember that you are responsible for your happiness, not hers. Helping her through whatever she is going through will only enable her to depend on you instead of taking care of herself or finding support elsewhere, AND it will keep your feelings tied to her well-being.
Good luck!
Yeah i know i'm responsible for my own happiness. I'm not helping her out in any way. It's just that i feel bad for her in some way. I'm actually quite happy myself. I see her almost every day and i'm thinking to my self: "you poor poor girl, you look like a mess. get help." But she won't ever do that.