Should I try to save thid friendship, or cut it off?

What do you do when you don’t know anymore whether you want to keep up with someone or just completely cut contact with that person? ( I know I’ve made similar posts in the past but the question keeps coming back )

Situation: I’m a 17 year old guy and my bestfriend’s a girl…about half a year ago, she started dating some guy and I just feel “forgotten”. Right now, my brains telling me to move on and considerate cutting contact with her but another part of me tells me to stay considering the fact ( I think ) I am a little bit emotionally unstable right now and don’t want to make a decision I will regret later in my life.