Dear Ariyike, should I send her packing?

Last night, I got a message from one of my readers saying she's been living with her boyfriend for three years and just two weeks ago, her boyfriend brought his female colleague home to spend the night with them because her appartment got flooded. The female colleague has been living with them in their one room appartment since then. Last week, this female colleague went to her "flooded" apartment to pick up some clothes and personal belongings and has since moved fully into this man's appartment with man and girlfriend. Female colleague now walks around the house in her sexy nightie and breast revealling clothes. The girlfriend is confused and doesn't know what to do. She said she has told her boyfriend to tell her to leave but he refused to tell her. She's asking if she should tell the girl to move out. Please advice her.