What should I do? HELP!

So I’ve been best friends with this girl for five years. (We'll call her Carla) We did absolutely everything together. We met at our local dance studio when we where 11 and we have been friends ever since.

Over the years she has had many relationships and I stud by her in every single one, but when every time she got a new boyfriend or girlfriend she would spend a lot of her time with them. I didn’t want to tell her felt I felt like she was leaving me out because I was afraid she would be upset. So I kept my feelings to myself.

Last year she started to date one of the guys in our friend group and I didn’t really like him. I knew I wasn’t going to like him as soon as I met him, but when she told me she liked him I decided I was going to try my hardest to like him. Sadly it did work.

He joined our dance studio so he could be closer to her and now I see him everyday. It’s like third wheeling everyday. Not that I’m not used to third wheeling on her dates and stuff, but EVERYDAY!

Lately she has been pushing me away. At first I thought I was just being crazy, but then she stopped hanging out with me. She started hanging out with one of the other girls at our dance studio. (We’ll call her Sadie). I wasn't mad because she can be friends with who ever she wants but then we all went to a mutual friends birthday party and sometime towards the end of the party she asked Sadie and her boyfriend if they wanted to go hangout that weekend. It wouldn’t have fazed me if she wasn't looking right at me when she was ”asking sadie”. I thought she was talking to me at first and I said sure and then she said very rudely “ I wasn’t talking to you” and turned to Sadie and asked her. I was so hurt, but most of all I was just confused. We have been best friends for 5 years why is she doing this?

It's been a couple months since the party and she still does stuff like this. I started to get fed up and I started to get closer to another one of the girls at the studio (lets call her Anna). We have been getting really close and I realized that my friendship with Carla is nothing like Anna and I’s. We have so much in common. We have deep meaning full conversations, she listens to what I have to say, she genuinely cares about me and our friendship, and she doesn't treat me like trash. With Carla she was always putting me down, always calling me fat, and telling me I'm stupid. I new the way she was treating wasn't right, but she was honestly my first ”friend” so I didn't know if it was wrong either.

I opened up to Anna about the situation and she told me I should and break things off with Carla. The only problem is I don't know how. Carla isn't exactly a ray of sunshine if you know what I mean.😬 If I tell her I don't want to be friends with her anymore she would totally make my life hell. Or even worse she’ll screw with Anna’s life and I dont want Anna to have to go through that. What should I do? Ugggh I feel so stupid. Did I just waste five years of my life?