for the evening in question she accepted a dress and tickets to the event the party needed access to.
spoiler from small favorMother Winter gave Dresden the unraveling and he asked if it was a gift or what, she said no it's a necessity. A Necessity can apparently skirt the binding rules of gifts that apply to fae. Also mother winter/summer had nothing preventing them from telling him they had no unicorn when he said he was sorry if he damaged their guard/unicpirn even though that information was what helped him realize something incredibly important, possibly setting the record straight also skirts the rules
Dresden's godmother goes to visit his place & check on him after he weakens the barrier between it & nevernever by dropping in on her rose garden & leaving a bunch of nifty stuff there under the daisies. When he gets back later from being interrogated by the fbi she has Susan & roger(?) suspended to the ceiling/walls and tells him that she simply put their demons to sleep when he asks what she did to them and says they were guests. He himself had not thought about the possibility of putting the demon to sleep but there was not technically a price for that exchange of knowledge(at least not yet) unless you consider it as payment for her "wrong" of assaulting his guests.
Nonspoiler version I think that necessities are able to trump the rules binding fae & that a small thing could potentially maybe cover a small past wrong/breach of etiquette if the recipient could have been considered the host. also it's possible that setting the record straight skirts the rules (spoiler forget the book)In addition to the small favor example above harry asks why Mab, The winter Queen of air & darkness would need a translator. At first she tells him that knowledge is valuable, but when he rephrases himself and makes it clear that the reason he was asking is because he wants to make sure it's really Mab she's able to skirt the rules and partly explain. You could say that perhaps the knowledge she took from him was the cost of that information, but there was no agreement for exchange and she gives it all back (even though michal/god did at least some of it earlier) saying that he could not have completed his task had she not taken the knowledge to keep him from using fire magic laced with the summer court's power allowing the gruff's track him with it
Even though ummm...Lady summer(fix?) was under a pretty serious binding preventing her from helping Harry even if it was to pay off her debt sold to Charity, but she was able to gibe him the butterfly to keep them warm &supercharge his fire magic as the warmth was a need to keep them from freezing to death & the summer flame was a need so the summer court could get Mab to pull her forces back so summer could retaliate against the redcourt for sending outsiders into their territory.