Nina There are no real words of comfort at a time like this but I too am so very sorry to hear of your loss - the previous posters have said it all.
I am sure your Mum is in a better place but, as I know from losing my Mum, there is still a massive gap in your life. Alzheimer's is such a cruel thing so it is a relief for Mum but it will take you a little time to get used to not having the visits etc.
My Mum died over three years ago and even now, we find ourselves saying "Wouldn't Mum have enjoyed seeing this?" or "Wouldn't Mum have loved that?" My advice, if any, is to keep remembering the good times.
I don't know if you have family but I am very lucky in that my husband, our own children and grandchildren (Mum's Grand and Greatgrand-children) feel comfortable to mention her name and we often laugh together when we remember happier times.
My thoughts, prayers and huge ((((hugs)))) are there for you