Dreaming of a messy room, especially a family member's, can symbolize feelings of chaos or disorder in your life or in your relationship with that person. Your sister's room being cluttered with trash may reflect unresolved issues or emotions that you associate with her or perhaps your own feelings of being overwhelmed. The cooking oil on her bed could represent a sense of something being out of control or not as it should be, as oil can signify slickness or difficulty in handling situations.

Consider how you feel about your sister and your relationship with her. Do you feel there are unresolved conflicts or feelings that need addressing? This dream may be prompting you to confront these issues or to clean up emotional messes that you’ve been neglecting. It could also be a reminder to take a closer look at your own environment and mental state to see if there are areas that need attention or organization. Reflecting on these aspects can provide clarity and help you navigate any underlying tensions.