I am so, so sorry that you lost your mom in that way. You did nothing wrong and it was not your fault! My mom died in April 2014 and it has been a very difficult year for me. I've only dreamt of her once, but it was very similar to yours. My mom's body was laying on her old bed, and was very cold and stiff. But I was so happy to see her!!! I laid down next to her and just hugged her and cried, and told her how much I missed her.
I go to a weekly grief group to help me process my feelings. Is there one in your community? Contact your local hospital to check. Also, Since you were not able to see your mom after she passed, I think it makes her death harder to take be because there is always the question ...is she really gone? Everyone grieves at their own rate and on their own way. I hope you can get some support for your very profound loss.