I understand why Theresa can't tell Ethan. Although we know what a liar Gwen is, Ethan thinks she is a honest good person. If Theresa were to tell Ethan, he might let it slip to Gwen. If Gwen knows she will call Juanita. Now once Juanita makes it to Harmony and Theresa knows she is there, I think at that time she should tell Ethan. Gwen's blackmail will be no good then.