So as some of you have read from my headcanon post(s), I am writing this Nowa as having a bit of a crush on Perrielle, but oblivious to it being reciprocal until the night before the battle of Gardhaven castle. I mean he still does go back to Kyshiri a bit after the war to help rebuild his village, then returns to Eltisweiss to join up with the Watch again. Now that they're both a little older, matured, and wiser (like early 20s), they might rekindle that little flame.
Which while some of the older lords and members of League might gripe and grumble over the Countess courting a commoner...that commoner also saved everyone's asses a few years back. Nowa is undoubtedly hailed as a hero in the League of Nations at this point, and probably is a figure of praise and hero worship among the common folk.
And I ten thousand percent think Perri knows that and will use that towards the nobility, "Don't care what you think, and besides you'd not be sitting where you if not for him so shut your mouth and let us be happy."
But also she is still a political creature, and while she does love Nowa-- this also helps in the way of endearing House Grum to the people of her County. He has the hearts of the common people, and that could be useful. However, it's not just her getting the advantage, through Nowa, the populace also has a voice to speak up for them. If there is somethign wrong or unjust happening, he's not going to be quiet, either to Perri as his liege lord or partner-- he can bring those issues to her more easily.
I'm pretty sure we can see this dynamic in play with his time as Commander of the Alliance-- Perri sat back and handled the political parts of the war while Nowa led the forces and inspired the people--I would argue that's how'd they work in peacetime as well. Nowa with the Watch, helping and listening to the people, Perri dealing with old farts in the League council, et cetera.
(I will say she too has a strong sense of justice so I don't think she'd ever be lacking there, but she may not be aware of problems when busy handling other fires. Or she may let her pettiness take over and laser focus on one problem, as it were-- she's not perfect in the least but she tries.)