I think your best tactic is to ignore, ignore, ignore this girl. My hunch is that she's doing this to get attention through a reaction from either you or her bf. I'm sure your bf is nice and everything, but I have my doubts that she's really going for him. Since she's going through a rough patch with her boyfriend, she probably is trying to show him "Look, I can get any guy I want. You should be lucky to have me."
I'd recommend making a pact with your boyfriend to ignore this behavior of hers. If she doesn't get a reaction, she'll move on to someone else to get her boyfriend's attention. I can almost guarantee that her behavior will become even more obnoxious and desperate at first as she tries to elict a reaction from you guys, but if you keep ignoring her, she'll move on to someone else. But I think if you say something to her and call her out, she'll just deny it and you'll give her the satisfaction of getting under your skin.
I couldn't agree w/NCShopper anymore. I totally think D is doing this for attention. She is trying to get a reaction out of you and probably trying to cause problems between you and your boyfriend because her and her boyfriend are having issues. Do not let her know that it bothers you - she'll do it more. Ignore her and like NC said, she'll eventually stop it because she won't be getting a reaction. By the way, I HATE girls like this! I've been through it before myself and I just wanted to kill the girl!
You really like her? Um, why? I think NCShopper is right, she just wants to get under your skin. But I'm not as nice as the loverly NC... I think you should have fun with it - when she bends over, I would totally be like, "Nice tits, girl!" And so on, whenever she pulls this crap. And I would TOTALLY tell her about some fictional girl at your boyfriend's work who is driving him crazy by curshing on him, then say something like, "Guys think it's so pathetic. It probably should bother me, but I know he's so annoyed it's just funny."
What's she going to do, get all upset at you? She's got nothing to call you out on, and you totally get to call her on being a sad, sad, sad little use-my-boobs-for-attention girl...
i totally agree with dizzy. sounds like she just wants attention and is trying to one up you because her relationship is bad and yours isn't. i love dizzy's idea of calling her out with "nice boobs." if she is totally passive aggressive, i would do that but act like its all in fun and jest. she should get the hint and feel like an idiot. if not, it could be really amusing for you and your boyfriend at least.