Insulting Mother-in-Law

When the Banta came home, his wife Preeto was crying. "Your mother insulted me," she sobbed. "My mother? How could she do that when she is on vacation on the other side of the world?" Banta asked. "I know. But this morning a letter addressed to you arrived. I opened it because I was curious." "And?" "At the end of the letter she wrote: PS. Dear Preeto, when you have finished reading this letter, don't forget to give it to my son."