Engrish

This morning on the bus there was a young Asian woman who was listening to a tape and reading an "English for Everyone" book. I looked over her shoulder to read her book, and saw this sentence: "You're sister is coming to visit." How is anyone supposed to learn proper English if the books are wrong? To add to the irony, the next page was a full lesson on "I am = I'm, you are = you're," etc.

I considered pointing out the mistake to her, but judging by the level of English in her book, it probably would have been a pretty confusing conversation. Besides, who would believe a stranger on the bus when your published textbook says something different?