How long does it take to get over the death of a loved one.?

My sister died last month unexpected. We lived together and one night she went to bed and the next morning we found her dead in her bed. She was only 50 year old and was going blind but besides that I thought in good health. We won't know for months what happened and I have a lot of guilt that I didn't get up sooner and find her sooner. by time we found her she had bed dead for abut 6 hours the corner said. She is the first person os close to me to die and I having a hard time dealing with it. Anyone know how long it