ocus on your work or studies
Did your friend stop studying because you don't talk with each other any longer? Does your friend seem depressed and gloomy all the time just because she is ignoring you? Has your friend stopped having fun in life since you both stopped hanging out together? The answers to these questions will presumably be a NO.
This will make you realize that there is no reason you should stop focusing on the important things in your life just because your friend has started ignoring you. If you are studying, focus on getting good grades. If you are in college, focus on all the activities that will kick start your career. If you are working, focus on doing all the things that will get you a promotion.
Focusing on the core activities in your life will help you overcome the feeling of being left out. It will give you direction and help to take your mind away from senseless peer pressure and social anxiety.