Mab cant touch Michael and his family and the Alphas are not on Mab's radar to be anything but a thorn in her side to be taken care of later.
Minor point, but as far as Mab is concerned, the Alphas probably count as effectively vassals of Harry after following him in the battles at the stone table and against the Fomor. She might temporarily require him to be isolated from all contact as on the island, but trying to break her knight's vassals away from him in particular is highly likely to be against Sidhe nature.
Plus, they're currently acting as bodyguards against all the threats that were previously cowed by not wanting to take on the Council or Ebenezar personally. Finding advantage in removing him from the Council is one thing, but even if she could plot to remove the knight's vassals, decreasing his survivability is bad business.