She held back details helpful to the boys, that is all. She lied to the 911 operator and to a cop that night but since then she has not changed any factual element of her story.
She is telling the truth here, she is credible when making statements that help the boys since she hates them. She is probably not going hold back now after she found out for the first time during the 60 minutes interview that one of the accuser's stories has Kim knowing about the rape and helping the boys dress here after the rape. (It is not clear if she yet knows that another of the accusers stories actually has her in the bathroom helping with the rape itself.)
The fact the the Police never asked her about her alleged participation in the rape makes it likely they never asked her about what happened in the car afterwords.