Question: Why can a non-Jewish maid sew her own clothes in a Jew’s house on Shabbos but she cannot write her own personal letter?
Background:
A. A maid cannot do melacha, forbidden work for her Jewish boss on Shabbos and the Mishna Berura 244:5:30 says that even for her to do work for herself is forbidden in his home so that people who see her shouldn’t say she is doing work for a Jew, I.e a maaris ayin issue.
Answer: When fixing her clothes everyone would agree it is obvious she is doing it for herself but when writing a letter it is not so obvious it is for herself.