That's true but also really not an argument for Mathilde to have any loyalty towards Sigmar or any Sigmarite institutions. Indeed a grudge wouldn't be inappropriate.
Do note that the Empire is a Sigmarite institution, before you go further.
Like it is pretty indisputable that Sigmar has been a net drain and entirely unhelpful. Maybe the meeting with the Ulricans will provide an opportunity to balance the scales...
This is untrue.
The conspiracy that was blackmailing Mathilde and her Master had it's members uncovered by Sigmarite Templars. Ranald put his finger on the scales of the investigation, but it was launched by an ex-Witch Hunter, and carried out by Sigmarite worshippers, trained by Sigmarite institutions.
The Grey Order killed them, but they didn't do the scut work.
Hell, the vast number of Stirlanders who came on the expedition here were also Sigmarites IIRC.
Polytheists, mind, but still Sigmarites.
Before Abelmar's death, Mathilde quite literally went to Kasimir, Priest of Sigmar, for healing after training accidents.
And I distinctly remember Mathilde and Kasimir using a mix of Divine Sigmarite magic and Shadow magic to slaughter the Singing King's army.
No complaints about Sigmar then.
Mathilde's grudge is personal, and colors her view of everything. Do not consider it to be gospel.
As the example of Thorgrim just demonstrated vividly, personal animus does not mean the other person is not doing as good a job as can be done.
I would like to remind you that the failure state of a theoretical "sacrifice Abel to free Mathilde" gambit is not "Van Hal died for no gain and the Sylvania campaign failed" but rather "Van Hal died for no gain and now Stirland has to deal with an angry and competent magic-user equipped with the Liber Mortis and a grudge against Sigmar". Which, knowing SV, would probably result in either Vlad von Carnstein getting revived or Belegar having to thank the living dead as a major reason Karak-Eight-Peaks got reclaimed.
It is an utterly unacceptable risk to take unless Sigmar was sure it wouldn't happen, and if Sigmar knew enough to make sure it wouldn't happen he would also know enough to ensure the same results would happen without killing Abel. Like my old suggestion of "clear Abel's crisis of faith via clearly divine/miraculous ressurection and then give a divine message to have Abel send Mathilde to help Belegar". We know that Gods can talk to their followers, and when Ranald (much lower on the totem-pole than Sigmar) is physical enough to let an random mage of above average piety know he was sorry for failing to save Abel, Sigmar sure as fuck can do something similar. Even if he has to go through Kasmir to do so.
-Perhaps IC Sigmar thought he had a better grasp on Mathilde's loyalties than you'd think.
Perhaps Abelhelm getting time to talk to stage a dramatic deathbed scene, and hand over both the Liber Mortis AND the list of conspirators who were blackmailing Mathilde was not entirely coincidental IC, even when no one else who charged the gates with him did.
Perhaps Sylvania was being Sylvania, and the gods don't act freely there without significant cost.
Or perhaps things really were that dire that such a gamble was considered necessary.
The confluence of a skaven civil war centered on K8P and a god-favored Grey Wizard making for the best chance of retaking K8P before the Karaz Ankor's battery reserves ran down is not a common combination of events.
Because do remember that the Dawi are a critical backstop for the Empire. If they fail, it significantly complicates the Empire's strategic situation.
-Order Gods, at least AFAIK, don't often talk freely to their followers AFAIK. Whether by choice, or because the worshippers won't understand.
Ranald's more social than many of the other male gods, but I have to point out that at Abelhelm's bedside, and for most of Mathilde's stay in Stirland, he did not talk either.
I get the impression that Mathilde's now-Heroic piety and special relationship with a fairly social god are very much skewing our impressions and expectations of the normal god-worshipper relationship.
-I can't swear to it, but I'm fairly sure that Mathilde has never been average Piety.
Average anything is around 10 IIRC.
She started around Piety 15.