Ok, I'll bite.
While it is true that she wants to rid herself of the shackles of Wissenland, this would be much easier in the current climate by doing so peacefully. Abdicating to one of the established families within Wissenland itself. Toppenheimers being the leading candidates, maybe the Pfeifrauchers.
She'd keep her status, but why and how would Wissenland keep the vote? That could and probably would throw off the current system. If Solland was a new entity, that would mean potentially 2 more votes that would be brought into the Sigmarite block. I'm sure Boris Todbringer and Valmir von Raukov would be pleased with that scenario (and if Helmut Feurbach is ever found alive)...
The vote lies with Wissenland, not with Nuln (This was different in editions past, but that has changed to a more simplistic standard where every province has a vote). None of the other city-states currently have a vote. Wissenland is tied with that, and without completely reformating the current electoral system, it wouldn't work. Each city-state would then demand a vote. If the Countess tried to keep the vote with Nuln, but then Wissenland, Solland or a combination of the two were then left behind, both would clamor for a vote, so it's not really conceivable to not let one of the new provinces not to have one.
So, why doesn't Emanuelle just give up her title of Elector since she doesn't want Wissenland anymore? Well, that doesn't work. Without the title, her shine isn't as bright, and she's no longer one of the dozen most powerful people in the Empire. She losses the tax from Wissenland, which she may be willing to forgo, but the title is really where it's at.
Karl Franz would be under too much pressure from multiple sides to allow such an even to occur, and the Countess would be committing political suicide by trying to pull off such a maneuver without support from some of the other electors (Helmut Feurbach may have been one, but again, is missing).
The current time frame is post SOC, and the north is already upset at Karl Franz for what they perceive as his inability to assist in a timely manner with repelling the Chaos invasion. It's a volatile situation as it is with famine, thievery and lesser nobles in that area making claims and power plays. All it would take for them to completely break off and start their own major insurection against Karl Franz would be to allow the Sigmarite block to gain more strength. As it is it's powerful enough, but adding more votes would ensure an Ulrician (or northern in general) Elector would never make Emperor. Sort of like a reverse situation for the American Civil War.
Such high stakes politics would need more than a little money, rebels, an old lost cause and an estranged captain to work.
Edit: I was able to add a little bit as I had more time.
