Mab can send any of many fae ladies to "prepare" Harry for the wedding. She could even do it herself. She could just send him to take Thomas' place with the swartalves for a weekend as part of a knightly duty. Or Lara could use Thomas' method . That protection is too flimsy to stand up to any effort to defeat it.
Harry has a really good reason to not want to relinquish that protection. On the other side of the equation, should Harry retain his independence from Lara's control, and do so in a public manner, that would put pressure on Lara to show that she is in charge; like a White Court Vampire should be in charge when they deal with a mortal human. The pressure Lara would feel wouldn't be much different than what her father faced when the porn director Arturo Genosa publicly defied the White King (Blood Rites), even though Arturo didn't know that was what he was doing by forming his own movie company.
Of course, there's a part of Harry that wants to ditch that protection, and it's not just the Winter Knight's mantel or Lara's succubae powers that attract Harry. He wants her. So it should be a really
hard frustrating time for both Harry and Lara to endure.
P.S. There is one aspect of the Winter Court / White Court alliance that I will be interested to learn about. Will the alliance be publicly announced while the Winter Knight is seen in the company of the de facto ruler of the White Court or will it only be publicly announced by the engagement of of the Winter Knight to Lara. You see I'm not sure what will bother Ebebezer, Carlos and the rest of the White Council more; Harry openly dating Lara Raith just because it looks like he wants to do so, and, or is under her control, or if his constant presence with Lara is understood as demonstrating the alliance. Ebenezer will be P.O'd no matter what the interpretation, but the rest of the White Council may be more upset by the alliance.
One more thing. One upside for Harry from the possible upcoming marriage is that not only would the White Council have to worry about drawing Mab's ire if they decided to move against Harry, it could be seen as a declaration of war against the White Court. Harry won't really be protected by Lara from the Council, except when he's at the Raith Estate; which isn't really a safe place for Harry to be, but I think the Council will still hesitate to move against a powerful wizard who is both the Winter Knight and the consort of Lara Raith.