She's officially a "camp follower". But yes, there is quite a bit of evidence (not just in folk songs) that women did dress up as men and enlist.
Yes there are many instances of Women participating in the Napoleonic Wars
- either in an official capacity as happened in the French Army with the
Cantinières.
Where each French regiment had women authorized to accompany it on campaign.
Called cantinières or vivandières who wore clothes of at least partly military design.
Their official function being to sell tobacco and refreshments such as cognac from
their carts and care for the wounded. In the latter role, some inevitably
ventured into harm’s way and became casualties.
Women at Waterloo
Or unofficially where women enlisted in the various regiments of the Napoleonic
armies as women, dressed up as men and fought for many years in their regiments
without being found out.
A few served with distinction and were awarded high honours and military medals,
like Sophie Dorothea alias Friederike Kruger. Who was awarded the Iron Cross
for her bravery in the Prussian Army during the Waterloo campaign.
Sophie Dorothea alias Friederike Kruge
On the Russian side we have the even more remarkable story of Nadezhda Durova
who enlisted in the Hussars ( again disguised as a man ) and became the first
known female officer in the Russian army - who again served with distinction,
being personally awarded the Cross of St George by the Tsar.
Her memoir The Cavalry Maiden, is a significant document of its era because few
junior officers of the Napoleonic wars published their experiences.
Her exploits were later made into a film called The Hussar Ballad.
Nadezhda Durova - Career in the Russian Hussars during the Napoleonic Wars
Finally it's perhaps no accident and no doubt only logical, that there are many
women serving as soldiers and horseman in today's Napoleonic re-enactment
armies across Europe and the UK. Albeit as women dressed up as men but as
mentioned above - history has set a precedent ( long before equal opportunities )
and their inclusion in today's front line forces.