Problem with that is she's not a Valkyrie, she's Einherjar. There is a difference

Tiniest Einherjar then. She'd be great in her own POV series continuing her quest against the bad guys.

Gotta say, I'm looking forward to the Tiniest Valkyrie series Jim ought to be giving us.

Yes, but just because there's evil, and someone knows there's evil, doesn't mean they're going to drop everything and potentially sacrifice their life and the security of their family to do something about it. 

How many times has Casa de Carpenter been attacked now?  The bad guys have shown up there, what, at least six books?  What are the odds Michael won't tell him, if he asks, that his own daughter was dragged out of the house by monsters?  That the panic room wasn't invaded in this last attempt?  That his youngest child was only barely spared from becoming a host to a fallen angel in the front yard?

I wouldn't blame the guy if he transferred out of Chicago after all of that. I certainly wouldn't blame him for not wanting to risk it all again and again.

At the rate Harry is going, he could invite the entirety of his friends and allies to live in Castle Dresden.

A few things I haven't seen mentioned that are worth noting:

Mab was proud Harry didn't give into the Winter Mantle. Then Murph dies and he does give in until the knights stop him. I say she DOES care about his mental/emotional state, because the last lady/knight for winter let the mantel run them which was why they had to be eliminated. It wasn't just about replacing the missing political link between the White Court and Winter, it was about trying to help Harry avoid the fate of the last Winter Knight. Mab has heavily invested in him and doesn't want it all spoiled by the death of one mortal.

And Harry just finishes lecturing them about making the situation right with the mortal world, when Mab decides he gets a replacement romantic interest. IMO, he kinda brought this one on himself.

And I strongly think she's planning something that has nothing to do with the marriage or politics, but needs both these two together. Call it fae foresight for the future books.

IMO both Molly and Harry may end up leaving the Winter Court in the future, after the coming implosion of the White Council happens, and both are safe from their threats. I can see Elaine becoming the Winter Lady in place of Molly. I suspect Harry will end up Merlin in the Post-White-Council meltdown aftermath, and him marrying his original love, Elaine as the bridge to Winter. Mab could potentially gain more by not keeping them on her team forever, but just sheltering them until the Wizard world gets it's crap together.

IMO, on Mab's sudden alliance marriage:

1. Mab is scared of a breakdown between her court and the white court due to Thomas being removed from the picture. She is also concerned Murphy's death may affect her winter knight in ways that make him even harder to control, and incorrectly guesses any woman will do as a replacement (Fairy thinking).

2. She is POed about how the Council has treated her knight, who is *hers* and is likely lashing out at them also.

3. She's also up to something, and I think she doesn't really think this alliance will go through as a marriage, but might be trying to get Dresden and Molly to work out their unresolved feelings. I think she's trying to give Harry a bodyguard not only due to the council threat toward him, but due some upcoming events where a super-powered girlfriend would be able to keep up and survive.

4. In the short story int he back, it looks like Mab watched Disney's Frozen with Molly, so I think we know where the sudden marriage idea is coming from there.