Can’t seem to grieve for my sister. Is this normal?

I lost my sister to lymphoma cancer last year and I can't seem to go through the grieving process . I have photos up what's app her everyday listen to her voice and even have her dressing gown with her smell on it.  but no tears seem to come (like the first few days) I'm not feeling anything. I want to cry. Some days I feel anger but I feel numb I just want to know this is "normal"