An emery board should do the trick, you need to hold the toe firmly though. Will she lie on her back on your lap without wriggling about too much? Just do one toe a day so that she doesn't get bored/stressed and gets used to the routine. If she wont stay still for you, swaddle her in a flannel or small towel so she can't move her wings.
Birds are so small and delicate that you feel you might hurt them but confidence and firmness is the way to go.