I'm an lonely 16 year old girl. With no friends and I'm feeling lonely all the time. How do I overcome this?

Set goals. Set a goal to do something with a friend at least once a week. You will need to reach out and ask someone to do something with you. It can be simply going to the mall, playing video games, going to a movie, whatever. Once you do it once, it will get easier. Try to do an activity that the friend finds interesting. If you have regular activities with friends, then you will feel better.