Unsupportive friends?

So, I don't have a huge circle of friends, but the few that I do have, I am very close to and talk to often. However, since I've been pregnant, I've been sick and sleeping a lot and I just haven't had the time to chat as much as I used to. I have told my good friend that I am pregnant, so she knows that this is why I'm hibernating, so to speak, but she has been so cold and distant to me recently! One day, she invited me to visit her campus and hang out till midnight, and I told her I couldn't that day; she got so offended, and she took it really personally that I didn't want to hang out until late! How can I express that honestly its nothing against her, and honestly I'm just trying to get through my pregnancy?  Is our friendship just doomed? I'm 12 weeks so there's still a long way to go....