Well, on that note, in case it sways anyone...
'Take up Van de Rijder's marching song to encourage and show solidarity with the troops.'
Let's talk about this.
This idea seeks to use one of the oldest morale-boosting tricks in the book: a commander presenting themselves as one of their troops. As an example, Roman Emperors did this so often - addressing the legions as 'commilitones', 'fellow soldiers' (following in the footsteps of one Gaius Julius Caesar, who leaned on this rhetorical device often) - that it essentially became a trope. This can create a sense that the commander and the soldiers are all in this together - that their pains are ones that the commander shares, that the commander's triumphs are their own triumphs - and thus that the commander is worth following because they understand the soldiers and are willing to go through the same things as they are.
Of course, this is a risk because it is, in part, a fiction. The commander is frequently insulated from many of the pains of campaigning that a common soldier might endure and is distanced from them by it. In Fanriel's case, she has going for her that she leads from the front and clearly expects to be in the thick of the fighting - but she is also an elf, at worst alien, at best different to the humans she commands, and she is afforded a luxury of shining plate and runed blade that the human troops cannot hope to have protecting them. In other circumstances, depending on how well she offers it, Fanriel might be laughed off or angrily dismissed as trying to present a falsehood.
But here? Here, apparently surrounded by ferocious enemies, with an 'us' and a threatening 'them' clearly demarcated, that falsehood is far closer to true - everyone is in this together, in the same place and facing the same danger, and must act as one to reach safety. A demonstration of unity is easier here and now than it would be at any other time. And by doing so in a way that offers a clear path forward - to fire the spirit and march on - which she herself is participating in, Fanriel not only offers something to focus on besides the present danger but also tells the soldiers that she will not abandon them to it and will instead face the uncertainty with them.
(At least, if she doesn't roll horribly. At this point I may as well be taunting Fate.)