In the beginning of HRT, the first few months one will develop firm lumps under the nipple area that slowly enlarge and soften. After a while the lumps become less noticeable as the breasts as a whole become more developed. I don't know if there is any specific definition of the lumps or what their role is, but that was my experience at least. At this point...about 2 years on HRT, I haven't noticed the lumps for a while as they've developed into just natural breast tissue now, although still growing [hopefully].
By the way, not to be nosy, but how are you coming into all this information about your friend? Do you both use a shared computer somewhere or something?