Again, this is assuming that the birth rate is low. This will only matter, if they are dying off faster than they are being born and trained. And so far, we have no evidence that this is even remotely the case.For now, that's my point, it won't stay that way if the elves continue to be mistreated.
There is reason for this speculation, Syl'anar supposedly has their slave trade as an important part of their economy, so what negatively affects the slaves, at least performance wise, negatively affects the economy. I don't think this is an issue of it not being a problem, more an issue of the owners in game not caring even if it is.
She could and it could prove very effective much like leaflet drops in previous real world wars were. A powerful propaganda tool that could swing things in her favor if not outright bring opinion to her side entirely. Better yet, get someone to go undercover with some of the more radical owners and catch them red handed doing something either blatantly against the reforms or that is borderline. That would at least gain the attention, and potentially the ire, of the people who wanted the reforms in the first place. Undercover tactics are a tiny bit shady, but at this point, I'd be willing to go full all out war with Nia as the commanding field officer of whatever force is involved, undercover work is minor compared to that.
We know many owners don't care, we know that most of the government doesn't care, many do, but most don't. Elf lives don't matter to them at all, and are happy to let them get hurt or die, and will only start to care, if and when it becomes a problem, and even then, they will only care about the numbers, not the people themselves.
This is like people going out and killing bugs that get in their way. Killing bees for fear of being stung or killing ants that get close to the home, not caring about how critical their roles are to a functioning planet.
--- --- ---
Yes, they would need intelligence and evidence for a normal campaign, if they want to get people kicked out of office, and gathering that intel would be a good job for Nia/Sui and the fairies. That said, most of these smear campaigns don't need facts, or evidence. Just make something up, say 'some people are saying' or 'I am just asking the questions, it's up to you to decide', and bullshit like that.
It is much easier to get people to believe a lie, than it is to convince them that they have been lied to.