my cat died

my cat died, she was ran over this morning my mum found her. I woke up to my mum sobbing i could hear her out my window i was rly worried bc she has mental health issues and i thought she was having an episode. But it was bc she found that our cat was ran over. I had to go to work an hour later i completely distracted myself but it rly hit me when i got home bc she was sat on my bed waiting for me. She isn't scratching at my door so she can run around my room and snuggle with me then run to my door to be let out after 15 mins. Our other cat is her sister and i feel sick looking at her they don't like the same but i just feel so ill. I just keep thinking she's going to come to my door.She was only three years old my head hurts thinking about her.