what about a trans women who is unable to develop breasts using hormonal treatments alone

I would be asking whether that makes her any different to any other woman who is flat-chested. All humans come with nipples and some sort of underlying fat/gland structure to support them. Not all develop substantial boobs, whatever their gender of origin or affiliation. I'm not convinced that large breasts are anybody's right, or that it is appropriate to have surgery to construct them. I do see reconstructive surgery after mastectomy as different, in that it is replacing what was already there and thus limiting psychological damage from the cancer.

Whether this stands up to rigorous logical enquiry I'm not wholly certain.