…Man, I sure hope Karak Vlag never catches even the faintest hint of that mess, or any like it.
I do not think Vlag would decide to grudge random peasants in Stirland, at the end of the day Mathilde is to the understanding of the Karaz Ankor a dwarf, which means she can decide on her own what her grudges are. Any sort of clear eyed analyses would conclude that she does not want to declare a grudge on the basis of what happened to her as a child. I think that they would respect that as they would for any other dawi.
Now what you might see is Vlag finding out about that and choosing to look more kindly on those who deal in magic close to their homeland, particularly when they have been cast off by their families. Vlag is after all a dwarf hold and that means they have vast amounts of money in their vaults which they could use to say help Kislevite male wizards to get to the Empire and join the Colleges (some of their appreciation for Mathy may well spill over onto them)