Could it possibly be not only the caring aspect, but something to do with equality? In some contexts it would be rude to make oneself tea and not offer to do the same for someone else who's there, although the therapy relationship is an odd one. Perhaps if you don't feel quite like equals, you feel you have to edit what you're saying carefully, as if talking to someone in a supervisory position or something like that? I don't mean that you'd think this rationally of course -- just wondering about other meanings / symbolism of her having tea and you going without.