Why do I get bitter and jealous when someone sings better than me?

I mean I can sing. I think I'm the best singer ever and even some of my family says I can sing but my choir instructor said my voice needs work and my singing isn't that good and I wasn't ready to sing solo. I told her my family said I was good. Then she said, "Well that's their opinion but I'm your choir instructor and I'm going to tell you the truth. You need to work on your vocals and you are not ready to sing solo." that hurt my feelings. This was in high school. I'm like a 4-6. This one girl I knew has an AMAZING singing voice and everybody was cheering for her and clapping for her. I didn't clap for her and I felt angry and bitter inside. She is like a 9-10. My teacher have her the solo. I said to the girl congrats but inside so wanted to rip her hair put. Why?!!!!!!!!! 😭😭😭😭😭