R.:
Unless she printed it, posted it or told a group of people - it's hearsay.
If she lied under oath, that's a different story. However, you would be hard pressed to prove it unless it's something very specific that you can prove.
People spread rumors all the time...they lie about people to feel better about themselves all the time.
You will know who your friends are if they chose to believe the rumors. Let her tell lies...what goes around, comes around. People will learn the truth about her. They will then start to wonder, if she talks like that about you, what is she saying about them? yeah...they will see her for the attention seeker she is...
Step back. Be nice. Just know that she is not your friend.
Good luck!!