Do you know the brand and model? Did she get the manual for the machine? Agree with suggestions to take to a dealer f possible. They will usually take the time to see what's up with the machine. Many feet can be purchased on line.
On some models, turning the hand wheel a certain locks the tubes so it can be threaded.
Again the manual will show directions and how-to for the machine. If a recent model, the manual may be on-line too.