Thanks @nomad-magus for the advice truly she has to focus on making her life better the mere fact she is her sis but still she won't marry her so she has to flow with her own trends and those thoughts of guilt will lead to indecision where will not be able to decide which party to stay with so she might have to let go of one side and at the end of the day she needs both people in her life .I feel her sisters'pain may be there is pressure from her family society has brought us up telling us at 26 you must be seeing some one and more so the african culture has taught us by 25 you should be married and when you turn out with out marriage every one questions your abnormality anyway let her put the pressure behind her back like you said before matching is done in heaven let her be patience alittle her life partner will come ,he is just around the corner.