The word prodigy applies to Waverly due to her being especially good at chess, or whatever it was she does. Her mother's point of view on prodigy is being the best she can be, and the term applies to her mother by not being quite as smart as her daughter.
The answer (after 2 hours of deciphering...) is
"THE TONGUE IS THE ONLY INSTRUMENT THAT GETS SHARPER"
Hope I could help, this was a tough one.
I don’t know if this is right but I think it is a metaphor if it isn’t I am sorry