New dog refuses to go down any stairs?

My boyfriend and I just adopted an 11-month-old Australian Shepherd. She is great with people and other dogs, but was never really introduced to a home environment -- she lived in an outdoor kennel/barn on a farm up till two days ago. She has accepted going upstairs, but we keep having to carry her down. We live on the second floor of a building, so this we can't just settle for her deciding to stay away from stairs. When she even sees that we're nearing the stairs to go down, she starts pulling and running away. How do we get her over this?