I mean, there’s also the point that all free-willed Undead are welcome within the Forsaken, so long as they work to advance the Forsakens’ goals and avoid bringing undue harm to their people.
Calia is doing just that. She’s won over two of the members of the Desolate Council, and won the begrudging support of the other two, and actively and publicly refuses to take any sort of overt leadership role. She’s helped reverse the Banshee Queen’s defilement of Lordaeron, the one last thing the Forsaken could truly call theirs, now and forever, and has made huge sacrifices for them, both trying to reconnect them with their living families, a thing many Forsaken yearn for, if only to find closure and move on with their Unlives, and dying for it at the now-revealed malevolence of the Banshee Queen, and the massacre of the Old Desolate Council at the hands of the same Banshee Queen.
And while the loss of Gilneas is a blow to the Forsaken who lost friends during the campaign, who saw this as a totally justifiable war against the Gilneans for their King’s refusal to aid his old allies and allowing thousands, if not more, to die pinned between his ‘Great Wall’ and the Scourge army that was not even shot at once by the defenders on that great wall, the Forsaken cannot hold Gilneas, especially not with such horrendous losses during the War of Thorns, and the loss of all the Val’kyr, meaning no new Forsaken brought into Unlife and no old Forsaken revived. It was a cunning tactical ploy that both divorced the Forsaken from the conflict as much as possible, and showed they had no interest in continuing a ‘needless’ conflict, averting or diverting the Alliance’s wrath by conveniently shoveling all the blame onto the shoulders of the former Warchiefs, Garrosh and Sylvanas.
In-Universe, I don’t think Calia, or Cauliflower as I like to call her to stir people up, is a massively-beloved figure amongst the Forsaken. Respected, yes. Thought fondly of, as the sole surviving Menethil and the Heir to the Throne who refused it for the sake of love, when she was alive, and again in Undeath despite still working on behalf of the Forsaken. Her status as a Light-raised Undead will certainly raise eyebrows, and ire, as many Forsaken felt the Light ‘betrayed’ them when it abandoned them to the Scourge, and then despite many attempts to be ‘resurrected’ as one of the Living, it never worked. The Holy Light scorned them and burns their bodies, despite their faith, their devotion and all their belief, and then it turns around and raises an Undead, and she’s whole, and pure, and almost Human, while they are shambling, slowly decaying mockeries of everything they once were.
She’s a breath of fresh air to the Forsaken, and a harbringer of change and invigoration to their people, and I am eagerly looking forwards to the drama and intrigue she brings to them in the expansions to come.