That's true. Sally was so ecstatically happy that Betty couldn't help herself — she just had to smile and be pleased. There's so much grimness and repressed emotion in Mad Men overall that a scene like this one just jumps out at you.

Beatlemania
Betty smiled and seemed sincerely happy when Sally told her she was going to see the Beatles at Shea Stadium. I've having a hard time remembering other times when she took such obvious delight in her daughter's happiness. So maybe there really is a mommy heart beating somewhere underneath that hard…