I am so sorry for your loss. I know that phrase doesn't help much, but I hope you know someone cares. Lou Gehrig's disease is a horrible thing to watch happen to someone you love. I had a good friend who passed away many years ago from it. I cannot imagine how it is for you, losing your mother. I do know how it is to lose your friend though, and I think the pain is similar in that it is intense and deep. I have found poetry to be a great solace for all that ails in my life. I hope you find that same comfort I did.
I think the poem is good. A little rough around the edges, but it expresses your emotions well. You give the reader a glimpse into what it is like to wonder if someone, or something, they love can be lost in a matter of hours.
One thing that I felt was extraneous in the poem would be the dementor. I think you showed the image of life being sucked away by a vampire, and the dementor lessoned the impact of the first image. Just a thought, take it as you will
Thank you for sharing, it was indeed something I am glad I took the time to read.