The answer lies in the future roles planned for Molly Carpenter. Mab's desire to have her and Harry positioned for future work is the driving force of the story.
I don't buy it. Mab is simply not interested in who Harry is training. Unless I see more, I don't think so.
My theory is that Charity is a descendant of Titania, an Molly was being groomed by Titania for the Summer Lady position.
First of all, the weather is mentioned as it usually is with Fairy Queens around. It is a hot summer. One could conclude that Titania is in Chicago.
Second, Titania hates Lily. Lily is the Summer Lady because Titania didn't plan for Aurora's death. Mab, on the other hand, is basically keeping Sarissa around offpage for this reason (as well as a connection to humanity). So, grooming Molly for Winter Lady at this point doesn't make sense. Mab HAS a spare. Plus whatever covert grooming Molly received emphasized emotion over reason (such as using fear to change minds).
Remember this is all kicked off by a letter from the Gatekeeper. We now know that he hangs with a lot of folks from Winter and is working with Mab to defend the Outer Gates. His message was about Black Magic in Chicago. Harry gets this message right after the execution of a Warlock.
If so, that's an awful roundabout way to get Harry to look for black magic. I think we must take Bob's theory as fact for now: Rashid could not tell Harry more. Also, they spend an awful lot of time discussing time travel for it to have no effect on the plot. Jim's a lazy writer. He wouldn't their in time travel rules for no reason.
Molly, at this point, is a Warlock and clearly on a downward slope. Charity admits that she had problems and future events (particularly TC, Changes, and GS) show that Molly is touched by darkness. Imagine that Harry does not act. I would consider it likely that Molly would be full Warlock and be executed. The primary outcome of PG is that Molly is saved from immediate Warlockdom and is Harry's apprentice.
Molly is tricked into creating fear anchors, which a fairy queen uses to send the fetches to kidnap her. I suspect this is Maeve, who is trying to subvert the gullible Lily. Realizing that Titania is creating a spare, Maeve seeks to destroy it before it's useful. Mab, however, suspects that Maeve is subverted by the enemy, and summons the Fetches to her with the girl that Maeve is so interested in. This brings along Harry and only THEN does Mab know Molly's importance. Her choice for Winter Knight. Titania's choice for Summer Lady.
The entire scenario would be set up for Glau to monitor Molly's progress to evil. I agree with Harry that Glau was a cutout and that leads to the answer to the next two questions.
Glau doesn't know Molly exists. And even if he did, how is he both monitoring her and a decoy? I suspect that Glau was a secondary fear anchor in Maeve's plan.
Mab sent the fetches to kidnap Molly to keep her away from the Black Council. They were upset enough about this that they attacked Arctus Tor.
Except the battle of Arctis Tor is finished when the rescue party arrives, and Molly is still there.
That means it is Mab that fixes Little Chicago. She does so because she wants Harry to succeed in his rescue. This is similar to the help she gave him by calling Thomas in CD. I want to point out that this plot is similar to (in some ways) the Archive in SmF. Mab tried to kidnap the Archive so that the Denarians could not (and failed). In the PG case put Molly in instead of the Archive. She does not make these things easy for Harry (remember the line about preparing Harry to become Winter Knight).
Mab doesn't seem the type. If her damned fool wizard is going to blow himself up, he's a weak fool and she doesn't want him.
The other thing that gets accomplished in PG is that Mab shows Nemesis to Harry. He does not recognize it but it is called a sickness and several nFected sidhe are part of the story. If Mab is listening in to the conversation at Mac's with Maeve, then she would know that Maeve in nFected right then.
Mab almost certainly figures it out in this book. Next we see her, she is still too mad to speak without killing mortals. My guess is that Maeve subverting the Eldest Fetch is what proved it, if not how Harry managed to smuggle Summer fire into her domain.
Finally, Ace likely is the one that hits Harry's car. He is likely the bomber of Murphy's car in WN.
That is much too simple and too pat for me. Elsewhere I said I think Lash made the whole car accident up. Harry details Lash's illusory powers directly before it happens and there are no witnesses. Why?
Future Harry is living in Harry's brain for the duration of Proven Guilty, and the accident is to fake a concussion to explain away Harry's limited mental real estate. He's who Lash speaks to when Harry's asleep, and he's who fixes Little Chicago. He's why the author hits us with a giant clue bat that says "TIME TRAVEL." I don't know to what end, but expect a future book will clear this up.
