Dreams involving significant events like the loss of a loved one, especially in a tragic manner such as suicide, can be deeply emotional and complex. In your dream, the themes of loss, obligation, and communication may reflect your feelings surrounding your sister's passing and the impact it had on your family dynamics.

1. Loss and Grieving: Your sister's suicide in the dream may symbolize unresolved grief or feelings of guilt. It could be your subconscious processing the trauma and emotions related to her death.
2. Marriage as an Obligation: Being made to marry in place of your sister suggests feelings of pressure or duty that you may feel in your waking life. It might reflect your concerns about family expectations, particularly in the wake of such a tragedy.
3. Communication and Warnings: Telling your jiju about the potential for death indicates a desire to express your fears or concerns about the situation, but his disbelief could symbolize feelings of helplessness or frustration. It might reflect your anxiety about not being heard or understood regarding your feelings and experiences.
4. Symbolism of Death: The mention of someone dying could represent a fear of loss or change in your life. It might also signify a need to confront and accept difficult emotions or situations.

Consider reflecting on how these themes resonate with your current feelings and experiences. It might be helpful to talk to someone you trust about your emotions and thoughts surrounding your sister's death. Processing grief can take time, and seeking support can be beneficial.