Your situation sounds so similar to the one I recently found myself in. I was orienting a nurse who had many more years of nursing experience than I did, said that she was charge in small and large facilities. She didn't have a wonderful reputation (actually it was downright bad), but I gave her the benefit of the doubt, thinking that she simply needed a better fitting job to be happy. So far, she has done well.
Sometimes people WANT to see newcomers fall on their face (think of the way student nurses and med students have been treated in the past) because back in the day, they themselves were 'thrown into the pit' with a sink-or-swim mentality from their preceptors/professors/instructors/attendings. This mentality has by and large dissipated, and preceptors WANT to see their orientees succeed.
Keep giving your orientee the tools that she needs to be successful. You are doing a great job by not joining in the gossip. Don't be nervous that you are orienting a more experienced nurse-nurses who have been in the profession and switched to a different avenue of nursing understand that they have to be oriented. It might SEEM like you are being tested, but from your accounts, you seem to be passing with flying colors! Keep up the positive attitude and keep giving positive reinforcement to your orientee when it's due.
Good luck, and stop worrying yourself!