Indeed, one of the greatest thing a woman can do for her man is allow him to put his head between her boobs like that. Especially in public.
What a great girlfriend. I just hope she says playful. It's not good if she becomes burnt-out or cynical.
The boob-rubbing is only good for me as long as the girl realizes is a gift to the man, not a way for her to assert her dominance over the man. Does that make sense?
I mean, everybody enjoys something. The issue is whether a partner in a relationship gives their partner what they enjoy out of a motivation of love and care, or whether they do it either expecting something in return, or they do it just to assert dominance or point out the weakness in the partner.