I just booked a ticket, full fare economy and premium economy, for a relative on EVA Air. As she didn't have an EVA frequent miler number, I left that mileage area blank. Now that I reflected on the booking, I should have credited it to another Star Alliance member, United Airlines, as miles don't expire vs 18-months for Air Canada. Before the flight, how do I link her flight to her United MileagePlus account? Should she just ask the check in agent to help her credit the miles to her UA account?

Thanks.