My sister keeps telling me to kill myself

My sister and I are both high school age and we share a room. I asked her to turn the light off because I was trying to sleep and she told me to kill myself. It's not the first time she's done this either, I know it might seem stupid but those kind of things add up. The next day when dinner was ready I stayed upstairs and waited for my sister to leave the table so we didn't have to sit next to each other because I was still really upset. I told my parents and they said they'd talk to her about it, but they also thought that I should get over it. They talked to her and she didn't care that I was hurt by her words in fact she seemed quit smug about it and laughed it off. Ive mentioned to my parents multiple times about feeling depressed and I was told I was to young to be depressed and to just be happy. 🤦 Gee why didn't I think of that