Friends jealous of my teacher?

My teacher from last year insists that she drives me home from school even though I live on the other side of town, calls and texts me, invites me to her house a few times a week, buys me gifts, and asks me to have lunch with her every day at school. I'm a female junior in high school, she's in her thirties. She also told me about sex and what it's like and that she loves me. I enjoy my time with her and my parents don't mind, but my friends are jealous and say she's obsessed with me. How can I make them stop?