I think she's stringing him along. Purposefully or accidentally, I don't know.
My advice to D: Call her out on it. Tell her how her behavior affects you and see what she says. She may not be aware of how confusing it is to others to see how she is acting. Maybe she is really confused about her sexuality. Maybe she thought she was into you, then realized she is only interested in women at this point and thinks it would be easier on you if she just makes excuses instead of being honest with you about it. Maybe she is really into you but doesn't think the relationship dynamic you could offer her is what she wants right now. Who knows? If you can't get a straight answer out of her and there is no ending to this in sight, I would cut my losses and focus my energy elsewhere. If she decides she interested and ready to pursue something, gauge where you're at then. Don't hold out hope for something that may never come, though.