How can i convince my mom to let me go?

Okk so theres this local festival thing in my town and its tommrow and its fun to hang around its got rides and stuff but its a little trashy and kinda ghetto but its fun! And my mom wont let me go without her being there. Im 15 and im very responsible and she claims she trusts me but my friend wants me to go to the fair with her, how can i convince my mom to let me go?!