I agree too guys...Servo is the way to go for photographing the handsome young lad who is probably moving. She hasn't said yet which AF mode she was using but if she is focusing and recomposing then Servo could be precisely the reason that she is missing focus.
Focusing and recomposing is a technique best suited for One Shot AF mode(I know C.Fcns can help here, but that gets complicated). Generally speaking, don't try to focus and recompose when using Servo AF.
This is why I asked earlier which focus mode that she was using, but she hasn't answered yet.
AI Servo would work for focus-recompose if she uses back button AF and releases the button after focusing, but, as you note, we don't have enough info. to know exactly what she's doing.