I'm having some trouble understanding this one.
Can anyone explain it to me?
She has been practicing some game or instrument often since she was four years old
If you are asking what it means, I would say it means, "She has played [football or another sport] since she was four [years old].
but not an instrument?
Anything that you can play. Games, sports, instruments etc...
Has anyone tried "She has been playing since she was four" and had it accepted?