When Ferrus told Folly not to become friendless like her mother.

Her mother is clearly Cavendash???

Also, we have any speculations on who the angels might be?

At the end of Cold Days, the conversation between Harry and Kringle led me to believe there is a way to shed a mantel other than the stone table. "It was Halloween, Dresden. You put on a mask for a time. That's all."  He looked directly at me and said, "Many, many mantels are worn--or discarded--on Halloween night, wizard." "You mean masks?" I asked, frowning. "Masks, mantels," Kringle said. "What's the difference?" He winked at me.

Also, Jim has said the Faerie courts only follow the letter of the law.  Being how my brother and his wife are both attorneys, there is a loophole in pretty much every law and if anyone could find it Dresden can.

Lastly, in Robert Jordan's Wheel of Time, Aes Sedia weren't able to lie.  However, they could still speak untruths if they; witnessed an event wrong, believed the statement to be true, and ect.  As we have learned many times in this series knowledge is power.  Being able to discard a mantle is probably one of the closest guarded secrets.