Hopefully this thread won't degenerate into anti-transgender comments like so many others today. Obviously Manning has needed mental health treatment for quite some time. Hopefully he can get what he needs while in prison. It's just too bad that prison is where he has to go to get help.
I don't see how the taxpayers should pay for this. One of the reasons the comments are so negative is because it feels like a smokescreen and/or a last attempt at sympathy. I don't care if he wants to become a girl, but he should wait until his/her time is served. I wonder if military prisons are monitored/protected any better than civilian prisons when it comes to that 'other' stuff.
Gender identity disorder / gender dysphoria is a genuine medical condition classified in the DSM (IV and V). For many sufferers it is not a matter of simple "wanting" to change their gender.
If you accept that gender dysphoria is a medical condition (as most in the medical and mental health professions have), then the question becomes "should prisoners receive treatment for it?"
I would argue that yes, they should. But I live in a country with socialised medicine, where healthcare is provided to all free of charge (including treatment for gender dysphoria). In my mind, being imprisoned deprives you of liberty, but not the right to free healthcare. I imagine many people in America would feel differently - "why", they might say, "should a prisoner get treated for free when I can't afford my own medical bills?".
That said, it's not totally clear to me that taxpayers would be paying for Chelsea Manning's treatment? I couldn't find any reference to it in her letter, merely that she hopes to begin hormone treatment shortly.