The Girl in the Red Dress appeared in Dreamer of Parasite Dolls. She is believed to be a hallucination seen by Eve, a memory fragment leftover from the human's emotions who were grafted onto her. Eve followed an illusion of the girl and walked off a ledge, plummeting to her death.
It is hinted the girl is not just a hallucination though as she closed Eve's eyes after Eve's death and vanished, laughing. She then turned into a scrap of red cloth and flew away on the breeze. Dreamer also opened with the piece of red cloth falling from the sky towards Megatokyo. The girl also registered on Eve's optical scanners, a hallucination would not have, though she registered as neither human nor Voomer.