I am a 15 year old girl and my mum died of cancer a month ago?

Im 15 and my mum only recently died of cancer-she had multiple kinds, , liver, thyroid,back it was basically everywhere and she also had a small brain tumour and i was just wondering how are you meant you grieve? I had known about her cancer for about five years and it had only just started getting very bad, she seemed alright until about a week before her death, she just started going downhill really fast then. Her feet and stomach/abdomen area swelled up very big and her eyes and skin got a yellow tinge. She started losing weight very quickly, in a few weeks her arms were tiny and frail, and her ankles and stomach were a stark contrast. I saw her being taken away in an ambulance and getting put in a hospice because we didn't know what else to do and had done all we could for her. She couldn't even hold a cup. And now, less than a month after this, my life is just continuing on. And it feels wrong. Like I have somehow cheated someone. Like my mum. I should not being living this so called 'normal life'. I should be miserable and swimming in my own tears. Is it because I did not love her? Im sure that I did. She was my mum. She was basically my whole world, I don't have a dad. But if I did love her then why did i not cry at her funeral?? Why and how did i stay stone faced just wishing that the whole charade was over. I just want my life to go back to normal. I try to think about her, but I cant even remember what her face looks like without a picture to guide me. Is my memory that bad or is my subconscious merely trying to protect my conscious from these haunting memories. I cant remember that past life that only occurred up to a month ago. Why is this?? Please help