Fear of Letting Go

I went to therapy yesterday and balled. My mother has a new boyfriend and it has triggered many emotions. My mother is a diabetic and was in a coma a couple of months ago. I am afraid to leave her home for long periods of time. However I am ready to move out. I have mixed emotions about the entire situation at hand. She has this man and he dont help do anything and she worships him and forget about us. My sister came home and told my that she saw this guy with another woman and my mother didnt believe her so that triggered fellings for me and my sister. Our step father abused us. He is now in jail. My sister left and moved to a shelter and I feel bad..I feel like my mother betrayed us she promised us that she will not let us down again. I am trying to move on and get better but I feel like I have to take care of my mother and if something happens to her I will feel bad.