After Peter messed around with Sarah (when he and Rachel were technically together), Rachel was upset at first but then eventually forgave him in the end.
First, why would you go back and tell Rachel anything? All men, or most anyway, wouldn't of said nothing. Personally, I didn't think Peter owed Rachel any explanation at all. It was a whirlwind romance and he was going back to L.A. anyways. I thought it was a stupid move on Peter's part. You had to go back to Sara and try for the pity f@ck. The good ones usually give in.
Exactly. There's no need to tell the truth. Unless Rachel asked point blank. He didn't sleep with Sarah. Nuff said. It was a silly plot device. And unrealistic. What man would ever say all that when nothing really happened.