Is she riding a frame you've tried wicks? Felix got 10 teeth difference out of his create (iirc), so it is possible.
But 20 to 14 seems a lot, so I do agree, it's unlikely.
What's your chainring? Maybe make it smaller and you'll need fewer teeth difference for the same effect, or have a double chainring (with bashgaurd) and if you go up the same number of teeth on the chainring as you go down on the freewheel, you have no net difference.
Is she riding a frame you've tried wicks? Felix got 10 teeth difference out of his create (iirc), so it is possible.
But 20 to 14 seems a lot, so I do agree, it's unlikely.
What's your chainring? Maybe make it smaller and you'll need fewer teeth difference for the same effect, or have a double chainring (with bashgaurd) and if you go up the same number of teeth on the chainring as you go down on the freewheel, you have no net difference.