Dealing with Grief and Regret Over a Loved One's Death

How can I deal with grief and regret over death? My grandmother died on June 23rd of last year and I still struggle greatly from the loss but what hurts me the most is the regrets I have from that day. When I would begin to cry, I would leave the room so she would not see me. I could not contact my friend in time whom she considered her grandson so he did not get to see her one final time due to me. The weeks before I could not visit her because of the distance between us and I had work so our final few hours together were her in a barely function state and her final hour she was in a awful state I would never wish anyone to see. She died in front of me and I have had that weight on me since that day. I love her and always will and I know this is why I feel such strong grief, but I have not gotten any better since her death. Please offer me some help in my journey to healing from this pain.