How to deal with the loss of a bestfriend?

My bestfriend and I have been friends for 4 years.We've had arguments but we've always put them aside for our friendship.During freshmen year I got into a relationship and began to forget about her and I admit it,i did. but I didn't notice it until she decided to cut me off without telling me.I was so hurt because she started talking bad about me behind my back to others.Eventually we worked it out and remained close until sophomore year.I had lost my virginity then and did not tell her because I thought she would find it disgusting and hate me (she hates talking about sex).So I told my other friends instead, ones who also had sex before.My bestfriend soon found out about it and confronted me.We talked it out and like always, decided to leave it behind. But after that incident I felt like she replaced me with some people she just met this year.Gradually she texted me less and I became the last person to know about things. When I forgot about her,Istill talked to her as usual and completely divided my attention afterwards.Imade an effort to change because she was my bestfriend. But I feel as if she holds a grudge against me for not telling her and has decided to secretly end our friendship. Every time I see her with her new "best friends" I can't help but feel a little jealous because for 4 years I was the person who knew her the most.I've decided to move on and accept the fact that friends come and go but it hurts. It really does.This is killing me.How do I move on from this?