My friend left me!!!!!?

Okay so this girl moved from New Mexico and we became like best friends. Then on a weekend we went to the mountains with our whole grade and our cabin was right next to the "popular's" cabin and she started hanging out with them and she left me and i want to say to come back to me and hang out wih me but i think shes changed for good. ANd she hangs out with them for everything now. So does anyone haven any good ideas on what to say to here. Should I just end our friend ship cause we still talk but not that much . Should i end it or try to get her to come back to hanging out with me???