The best way is for YOU to model the correct way to speak. She will hear the wrong things from many people, but do not panic. I would explain to her gently that what she is saying is not positive, and then you can tell her what you would like her to say in its place. You can tell her you don't want to hear her say ... around you.
But be aware that a lot of kids just practice saying what they hear and at that age it is really not doing them any harm. More experimental speech than anything.
Listen to what she says, don't over react, guide her as best you can...and know that she is in process. She may be just mimicking what she hears and not internalizing it. Watch for behavior that mirrors the speech (eg a tantrum and screaming"life isn't fair."
If she hasn't internalized it, she may not even know what it means!!