my co-workers talks about me behind my back to another co-woker. I'm very bitter right, how do I handle this

My co-worker just started working with me and she had to take over an account that I use to handle about 3 years ago. Prio to me taking over the account another young lady was handling the account. The new co-worker is finding errors and now she is blaming me and the other co-worker and is saying really nasty things behind my back. I work with this person closely everyday. How should I handle this. What was told to me was in confidence.
8

6