I had a yellow lab too and he was pretty much crazy. What you should do is somehow show her that there's nothing to be scared about the stairs. Maybe you could do everyday is put her front paws in front of one stair and if she does not put them back were they were before reward her with a treat or her favorite game and praise her. Keep doing that until at least she walks a flight of stairs. You could also by the help of someone put her in the middle of the stairs her front paws in one stair and the back paws on the other stair. Courage her to either climb or go down by showing her her favorite toy or her favorite treat or snatch something that she will get angry about and become posesive maybe she will snatch it off you..... that's all the advice I have, hope it helps a little (I know its a bit silly but with the most silly things that you have to make your dog do he at last learns well )