Maria,
How are you doing ? I also lost my Mom to cancer after a 7 year battle. Was very frustrated after all that, that the last 4 months were unkind to her, she never seem to get a break.
Additionally I lost my husband 7 months ago. I have a daughter.
The pain is like no other, and there is a journey ahead probably the same in some ways for you and your sister and your mom and probably in some ways different.
Keep talking if you can. Talk to your Dad, talk to others, talk to your Mom.
In one of the books I read another family called it "regular dreams or visits" Like others stories, don't think I'm crazy but I do have visits from my husband, he is calm and looks good. I get wound up, and even awake I can sense him with me. Sometimes I ask him "where have you been" when it gets long between times that I can feel him near. He responds the same everytime I ask him. "Right here"
My daughter wonders sometimes why I don't cry in front of others. That's just not me, makes me feel worse, it is okay to cry, but it is okay not to cry in front of others too.