These need to be requested in advance:
https://www.aa.com/i18n/aadvantage-p...vel.jsp#making
Contact Reservations or visit an American Airlines Travel Center to request a mileage upgrade award.
You may request an upgrade when you book your trip or at any time before check-in.
Side question: Do "American Airlines Travel Centers" exist any more? This makes me think of the off airport ticket offices in cities. I guess it could be a service desk in the airport too?
Good to know thanks! But I don't understand why she would pay 75 at the gate? Don't you pay upfront in miles and cash, even for waitlisting?