Chelsea Manning, whose role as the source of one of the largest leaks of US government state secrets in history earned her a 35-year prison sentence, will be spending her sixth Christmas in military custody with no end in sight for her ordeal.

In an article in the Guardian, the army private writes movingly about the feeling of detachment that engulfs her at this time of year. As her detention lengthens from her original arrest in Iraq in May 2010, she says that she is prone to existential doubts in what she describes as her “artificially-imposed stasis”.

“The chasm between me and the outside world feels like it’s getting wider and wider, and all I can do is let it happen. … I sometimes feel less than empty; I feel non-existent.”

It is unclear how many more Christmases Manning can expect to spend behind bars for having transferred about 750,000 files of US state secrets to the open information website WikiLeaks. She was sentenced to 35 years in August 2013 having been found guilty on 20 counts, including six under the controversial Espionage Act of 1917.

In her Guardian article, she says that one thing that gives her hope, despite her desperate situation, are the letters and cards she receives from supporters. “I am happily reminded that I am real and that I do exist for people outside this prison.”

Another source of comfort is that her appeal against conviction and sentencing is well under way. Nancy Hollander, lead counsel on the appeal, confirmed that Manning’s brief to the US Army Court of Criminal Appeals will be filed some time in the spring, setting in train what promises to be a lengthy legal process to review what is probably the harshest punishment for the source of an official leak in recent times.

Hollander said that along with her co-counsel, Vince Ward and Captain James Hammond, she has been poring over classified evidence in preparation of the appeal. A special secure room has been created within Fort Leavenworth, Kansas, where she is held, where lawyers and their clients are able to discuss classified material.

The US Army Court of Appeals is imbued with strong legal powers. It can dismiss the case outright, send it back for a new hearing or re-sentencing, or set its own new sentence.

“This is a very important court for us and we are focused on winning there,” Hollander said. “For us, winning would mean all the charges being dropped and Chelsea walking out of there; or it could mean Chelsea being given a much lesser sentence.”

This will be the first Christmas that Manning will spend since she began hormone therapy to transition as a woman. In February, the Army granted her the hormones – a breakthrough in terms of the military’s handling of prisoners with gender dysphoria, a recognized medical condition in which a person’s self-identity is in conflict with her or his biological sex.

Manning writes that the hormones have started to take effect. “The anti-androgen and estrogen I take is reflected in my external appearance, finally: I have softer skin, less angular facial features and a fuller figure.”

But the legal battles that she begun by suing the military for hormone treatment in September 2014 are by no means over. She continues to be held along with male prisoners in the maximum-security United States Disciplinary Barracks in Fort Leavenworth and is not allowed to grow her hair beyond the uniform male standard of two inches.

Manning’s lawyers, led by Chase Strangio of the American Civil Liberties Union, filed an amended complaint in October, pointing out that even the military’s own medical providers have recommended that she be allowed to grow her hair according to female standards. The government has countered with a motion to dismiss the complaint, and a ruling is expected anytime.

“Despite the many obstacles she has faced, Chelsea continues to fight for justice. So many transgender people in prison and jail are fighting for healthcare and fighting to survive and hopefully Chelsea’s fight will pave the way for more justice for more people,” Strangio said.