You ought to be.
Google says it's OK for them to read your email because ... well... because you shouldn't expect them not to. In fact, it's in their terms of service - you read that when you signed up, right?
In a recent court documents, Google says, "Just as a sender of a letter to a business colleague cannot be surprised that the recipient's assistant opens the letter, people who use web-based email today cannot be surprised if their emails are processed by the recipient's [email provider] in the course of delivery.