Sorry to be the one who has to tell you this but, she was probably talking to him while you two were together. He got eventually got her.
Advice from a drunk plate's_empty: move on. She'll get bored with him eventually and start pinging you. Just seeing what you're up to. Ignore.
Do you want her back?? Of course you do. Then by all means, when she starts hitting you up, do not respond.
Wait till she starts spilling her heart out. Then wait some more. Then make her beg. Then put her on as a provisional basis, like you'll only start seeing her on Tuesday. Then start calling her that....Tuesday.
Her: what are you doing?
You: Why are you contacting me Tuesday? It's Wednesday.
That's it. You're golden.