I know how hard it can be when you loose your mom to suicide (my bio mom). And you have an older sister whom you share a strong bond with. I remember my sister coming to see me when I was first diagnosed with major depression and my older sister crying while in the hospital not understanding (yet) why. Her being angry with your mom (because she took her own life and abandon you and or caused the SI somehow. You will learn how to heal without cutting. Let your sister cope with her feelings in her own way. That bond will never fade. I know it is really hard right now for the both of you but hang in there. This too shall pass. Not many share our unique life circumstance and I really felt the emotions in your post. Feel free to pm me anytime.