Hi Lizzy, so sorry for your loss , can I ask when your Mum died? It sounds like you're having a difficult time, talking about it here will help. Your dreams are your brains way of processing what it doesn't deal with throughout the day, that's what I believe any way. Watching someone die is a traumatic experience, no matter how peaceful the death, someone is gone, before your eyes.
I'm on this forum because my husband died, 5 weeks ago, he died in my arms after battling with cancer, although he was in a lot of pain it was a 'good' death compared to losing him in a car crash or suddenly with no previous illness. Even so almost every night he dies again, some nights he drowns, some nights he burns, some nights he is lost and I know he is dead and I can't find him, and I wake up with a start, feel relief when I realise it was just a dream and then the realisation that although the dream is over he is still gone, and I am alone in our bed hits me and that's sleep done for the night.
My beautiful Mum died back in 2002, I was with her when she died, and for a long time afterwards my dreams were difficult and disturbed. But in my experience they do fade, they soften and eventually they happen less and less often. Its so important to allow yourself to think and talk about the death too. I find now that if I have had a good cry during the day then I sleep a bit better. You cannot control your dreams, you cannot control grief although it is so tempting to try, don't force anything away, or try and make yourself think or feel anything, just go with how you are, if thoughts pop into your head, think them, feel them and then move on. Grief is the price we pay for the love we had and have lost and your dreams are part of that grief, it will get easier to live with, soften, become less raw, you don't need to 'learn' to live with it, you're doing that already, and you will be ok. xx