That's really strange! Why would she want you to be late to a session when you could, instead, be spending that time with her working on things. I'm always early - it's a good chance for me to decompress, think about things, and be prepared. Seems like an odd request unless a) the receptionist is somehow bothered or b) you are working with her on how not be so perfect (although I could think of better exercises). I've had discussions with my therapist about perfectionism and unrealistix expectations, but arriving early or on time is just plain polite and respectful.