She was not trans as being trans is a modern way of identifying yourself as the opposite sex and going through physical changes in order to look like it. She was just a remarkable woman whose story still interests us 500 years later because of how "modern" she seemed to be. This is because of the many misconceptions that still exists about the role of the medieval woman.
For example, people think that women were confined to the bedroom and the kitchen. This opinion comes from stories about knights in shining armour rescuing damsels in distress, and the concentration on male behaviour in film and literature about the time. Another false belief was that women were not warriors, and that this was one reason that Jeanne d’Arc was executed; for stepping outside her role in this way.
On the contrary, it was often expected that women would take part in battle. The fact that Jeanne d’Arc became a mascot for the French army supports this. Had fighting women been frowned upon at the time, then surely the soldiers would not have supported and admired her, let alone have accepted her orders in battle.
In addition, the fact that Jeanne d’Arc wore specially-built female armour shows not only the skills of craftsmen at the time, but also the confidence placed in Jeanne’s ability on the battlefield. So she never dressed like a man, or tried to pass as one.
Only when she was captured and sentenced for witchcraft and heresy by the English was she tricked into wearing men’s clothing in order to be accused of cross dressing, which then led to her being burned at the stake.
It's true that not many women went on the battlefield, partially because of the cost of it, but also because they had so-called ‘womanly duties’ to attend to. Jeanne d’Arc, even as a child, was proficient at spinning and weaving, as well as other feminine crafts. This was a fact of which she was certainly proud of, and indeed she told Jean de Metz, ‘I would rather stay at home with my poor mother and do the spinning’.
She never married because she took a vow of celibacy at the age of 13, a decision which reveals not only her religious nature (she spent much of her time at church) but also her knowledge of sex which she got from her mother.
At the age of 16 she was courted and proposed to by a boy from her town. Citing her celibacy as a defence, she turned down his offer. She remained a virgin and celibate until her death.
She was however accused of sexual promiscuity, a charge that was dropped after investigations proved otherwise. However, in recent times some scholars have stated that she was a lesbian. There is no evidence of this, and some state that there is in fact evidence to the contrary:
"An even more baffling misconception is the notion that she was a lesbian, despite the fact that this accusation was never even included in the 70 articles against her: if you read through these charges, you won’t find the slightest mention of this issue at all, nor will you find mention of it anywhere in the testimony (Cauchon [sic] accused her of a great number of things, but lesbianism was not one of them)."– Myths and Distortions about Jeanne d’Arc.