Why does my friend always want my attention?

This girl and I are friends. She gets super jealous when I talk to other people even though she’s popular. The reason she’s popular is because she is a really tall blonde, labeled the prettiest girl in school. I’m popular because of her, she basically told all of her friends that I’m funny. Anyways in the seating order in English I happened to be next to her. I was talking to another girl beside me. She then yelled at me and said “Shut up!” I asked “Why?” She said “Because you can talk to me instead.” I said “WHAT!!” She played dumb and said in a mocking tone “WHAT” The girl I was talking to was like ”....” Another instance is I was talking to the other girl again. She randomly interrupted the other girl in the middle of conversation and said “OMG, you’re Instagram was hacked” I said “Seriously! What did the hacker do?” She said “He commented on all of my photos asking for s*x” I was really surprised by this news considering I’m only 13. I was so mad at the moment. Then later that day after 8th period ended, these other girls got into it too. She came up to me and said “He also asked for oral s*x” I went home and went on the computer. There was NOTHING. I was so annoyed. Also she watches me every time I go to the pencil sharpener and feels free interrupting all my conversations by saying “Shut up”. The only time she doesn’t get jealous is when she sees me talking to my two best friends. Please help I don’t understand her at all. I almost forgot she always touches my hair and one time she asked me to hold her hand. I rejected,