Frankly, I've got some serious reservations about this whole idea of "mantles" and what's happened both to Harry and now to Molly. And frankly, I'm sick of fairy shenanigans and politics; they never interested me in the first place because there's nothing about them to connect with.
When Harry faced that choice in Changes, Butcher painted himself into a corner. The way he'd always portrayed the Sidhe, they were always beautiful, always completely amoral, and always soulless. If Harry agreed to become Winter Knight, he would have no choice in what he became; he had made his choice and anything Mab wanted him to do, he consented to do. So Butcher had two options: 1.) somehow let Harry out of the agreement on a technicality or contrive circumstances under which Mab would let him out of the deal in very short order or 2.) let Harry remain Winter Knight and become a monster. He tried to take approach 3.) try to make out that the mantle of Winter Knight "isn't so bad" and Harry doesn't really change so significantly. (Or will somehow get out of the mantle before he does.)
With all due respect, that's every bit as much a cop out as option 1 or 3. Harry agreed to anything Mab wanted. Anything. She might let him make petty decisions just because it's pointless to make every choice for him, but the only way that oath means anything is if Harry really does have to do anything Mab wishes. The vast majority of the Sidhe we've ever seen in canon were not just amoral but absolutely and completely and diabolically evil. They had interests and could even be cooperative given adequate incentives, but they cared only about power and pleasure. The only possible exceptions--and there's no way to assess to what extent they are exceptions--were on the Summer side of the fence, which Harry and Molly aren't. If you try to make being the Winter Knight not so bad, then you have to artificially rein in the evilness going on in the Winter Court (which is ridiculous) and downplay the seriousness of the decision Harry made. He gave himself up to Mab. He's her creature, body and soul. Yet somehow she'll tolerate him laying down the law about what he will and won't do and to whom? And she's just going to happen to never order him to do anything evil with all his power and ingenuity while he's in her service? And it just so happens that circumstances arrange themselves so that he doesn't have to do evil while he's in her service? Totally implausible. And I'd cry foul if Uriel or someone else were orchestrating things behind the scenes to arrange that because Harry has his autonomy and it's not for archangels or even the Almighty himself to intervene and manipulate the consequences of human choices after the fact or they're playing favorites and the choices people are given really aren't meaningful.
Sometimes, the most important choices we make in life aren't made in the way or when we thought. We do one stupid thing and then we find things going further and we're bound into the consequences of those earlier decisions.
But there's another big issue. I can buy the Knight of one of the faerie courts being human because he's granted power by the Sidhe and is beholden to them, but he's also their mortal champion and not technically (apparently) a faerie. But a human girl becoming Winter Lady? Mab's daughter and heir presumptive? Everything before has indicated that the Fae are fundamentally different from mortals and the role of one of the queens of each court can only devolve on a faerie or one of faerie lineage who chooses to renounce all other lineage and prerogatives. (Molly doesn't seem to be in that camp at all.) The way a queen's power passes--apparently without requiring consent--is just plain indefensible and horrifying on every level unless the candidate never starts off with a soul in the first place and wouldn't have to choose to be divested of a soul. And if consent is required? Then Molly's position is the more horrifying because she has just chosen to give up her soul--and on an even bigger scale than Harry, who at least remains mortal. Either way, are people actually okay with Molly becoming a faerie? I know I'm not. I think it's the worst thing that could happen to her, worse than death, because she becomes inhuman. And how? Associating with Lea? None of that makes any sense, and one would think that if anything Molly was doing was going to put her in this kind of situation, she or someone else would know. And seriously? She's heir apparent to Mab, but she could somehow get out of it? She and Harry can make irrevocable decisions but still get out of them? (I call shenanigans.) It's not that I want Molly to become like Mab, but if she doesn't become this conscienceless, soulless force of nature, then everything we've seen of the fae up to now is inconsistent and like a dog-and-pony show more than a reality. Not to mention that any fae has no room for loyalty to God as they're bound by the will of their superiors in the court, so becoming Winter Lady puts Molly squarely outside of any hope of salvation as far as the Church is concerned. Molly's parents and siblings would certainly think of it that way. Michael and Charity's reaction to this is nothing to titter or giggle about. Given their beliefs, they are losing their daughter in a way, and with a permanency, even death couldn't take her from them. Maybe most people don't think of salvation or damnation as realities, but devout Christians most certainly do. And anyone who drew their child into such a fate would not only be persona non grata, but a mortal enemy and certainly nobody they'd allow around any child they were entrusted with. Nothing in the world could ever make up for losing every eternal hope for your child.
(Though I think Butcher took Molly beyond the pale when she used magic to commit murder and if this is what Butcher does to characters I've invested in and cared about, making them dark, twisted shadows of themselves, I don't want to read any more. I believe in redemption, but I also believe these characters know a hell of a lot better than to do what they're doing and when you have that level of moral knowledge and power and commit the most heinous sins out there like murder anyway with that power, you may well, indeed, put yourself beyond the possibility of redemption. You're mocking mercy and the power of redemption and, indeed, spitting in their faces.)
In any case, as far as I'm concerned it's no fun to read if stuff like this is going to be happening. Am I crazy, or am I right to be wondering if Butcher has really jumped the shark here starting with Changes?