I have two best friends and they always leave me out?

I am in an intro cl at my new school. There are exactly four girls (including me) I used to be best friends with two of them whose names are Jenny and Lexi. The other girl is named Jane, and she is a bully, she makes me feel extremely insecure and she hurts me. Jenny, Lexi and I are best friends or at least used to be. I always liked Jenny better, and now she is ditching me for Lexi, even when I try to hang out with them, I feel secluded and lost. Jane is rude and I am now forced to hang out with her. Since I chose not to, I spend all my lunch and recess eating in washrooms. Jenny always like me better and now she does not. She goes out with Lexi and leaves me behind. Lexi, on the other hand does not like me. How can I make Lexi like me, so that I can hang out with both Jenny and Lexi?