She is an attractive brunette woman who wears a night mask when she sleeps.
Horbert's talking in his sleep, "having a nightmare," was staged for her benefit but he need not have bothered, because she missed it completely. She seems to be a heavy sleeper.
Scooby-Doo! Mystery Incorporated
She seemed to be completely oblivious from her husband's staged nightmare to his criminal activities as the Dreamweaver. In the end he told her in apparent disgust, "Go back to sleep, dear."