How can she? Even if he doesn't bother to shield his dreams, he is a warder twice over and thus protected, so she cannot contact him that way. She has no idea of where he is (and she did ask Aviendha after all) and no way of finding out reliably. Elayne is much better informed in that regard but she is restrained from getting in touch with him by practical considerations such as Aviendha mentions in the beginning of CoT when they first feel the Cleansing. If his own baby-momma can't relay information to him (as for example, the fact that she now has that particular relationship to him), how is Egwene supposed to?