Anyone with the confirmation number can check her in -- if she has a computer or a smartphone she can do it. If you do, you can email her a pdf of the boarding pass, or if it's easier she can just print one at the airport kiosk -- her boarding position will already be reserved from when you checked her in.

Yes, you can generally check-in online on behalf of someone else, provided you have their specific booking details. For most airlines, you simply need the Booking Reference (PNR) and the passenger's last name. If you are part of a group booking or traveling on the same itinerary, you can often check in all passengers simultaneously through a single session. However, to complete the process for someone else, you must have their passport information (for international flights) and be able to answer security questions regarding their luggage. Some restrictions apply: you typically cannot check-in a minor traveling alone (Unaccompanied Minor) or a passenger who requires special medical assistance or manual document verification. In 2026, many airlines also require biometric data or a "live" photo via their app for certain routes, which might require the passenger to be physically present with the device. If the passenger is on a separate booking, you would need to log out and log back in with their specific credentials to complete their check-in.