Consciously remove every bit of her existence from your environment. Get rid of everything that reminds you or her. Stop going to the same places (if possible).
Most importantly stop romanticizing your image of her. She doesn’t respect you, she doesn’t want to be with you, and she abandoned you like a toy she grew out of. Honestly, the way I get over exs is I hate them. Especially in the manner your girl treated you, you should hate her. She cheated on you while you were together meaning she didn’t even give a fuck if she hurt you. How can you care about someone who doesn’t care about you? That’s like giving a hug to someone who punched you in the face. Burn that image of the girl you cared about and remember the girl who hurt you.
You deserve someone who cares about you as much as you care about them. Someone who won’t intentionally hurt you. Someone whose happiness is you.