Talking back

I have a 3- year- old daughter and she has a very smart mouth. She is always talking back to me, and I am not sure how to stop this. My family says it is because I laugh at her. But, I can’t help it. Some of the things she says are really funny, but I know she shouldn’t be talking to me like that. Is this just a phase, and if not, how do I stop it now before she reaches her teen-age years?