YA ? book about a visiting aunt ? reciting idioms

[Melanie]

This was not the main plot of the book, but it's all I remember and have thought about this part over the years trying to figure out what book it was! I probably read it in the 80s.

There were two girls, cousins maybe? sisters? An Aunt ? or older female relative came to visit and she carried around a little book full of sayings and would pull it out and recite them. The girls couldn't stand it and plotted to steal the book so they could buy their own copy and contradict the aunt. For example, if the aunt said “many hands make light work” the girls could pull their copy and say “too many cooks spoil the soup.” When they finally got their hands on the book, it turned out to be homemade. The aunt had cut out these phrases and pieced together the book herself.

That's all I can remember!