Sunk costs and decision making

Alison has plans to go to a play and already has a $$50$ nonrefundable, nonexchangeable, and nontransferable ticket. Now Victor, whom Alison has wanted to date for a long time, asks her to a party. Alison would prefer to go to the party with Victor and forgo the play, but she doesn't want to waste the $$50$ she spent on the play ticket.

From the perspective of an economist, if Alison decides to go to the play, what has she just done?

Made an optimal choice

Correctly ignored a sunk cost

Incorrectly allowed a sunk cost to influence her decision