Our old golden retriever,wont climb the steps on rv

Well we made a ramp and put carpet on it, she put her front paws on it,,, then did a big u-turn and dragged us back to the house! We even tried her fav treat, some stinky canned cat food and she turned her nose up! Our vet said give the cosequin a good try but its been a month and no change. We would like to try the rimadyl, we have less than 2 weeks before our reserved camping spot on the St. Lawrence river! Thanks for your replies,, I would never have predicted our old girl would react this way. :(