Bane hadn't expected the turn of events that had occurred. Celeste ended up drinking far more than he had thought that she would be able to handle. Her tenacious spirit somehow wouldn't let her be beat out by him so easily.
Where it was pride or an honest desire to avoid spending time with him, the alpha wasn't certain. He just knew that for her health he couldn't let her drink anymore and thus much to many of the spectator's surprise conceded and gave her the win.
Alcohol made humans act weird or at least it made this one act that. Upon hearing him verbally admit his defeat to her, she laughed a little too gleefully. Making a remark about how he could no longer bother after this.