Joan was such a bitch last night. She's so mean to Peggy. I am not sure I can even remember an episode where she's nice to Peggy. I agree that she's probably mad that Peggy is successful when she started out as a secretary.
Could Betty and Henry be more immature? Henry is obviously jealous that Betty has feelings for Don that she's trying to hide. Betty is a spoiled brat that doesn't know what she wants in life and no one will make her happy.