Board Thread:Legitimate Canon Questions/@comment-27547895-20160203223511/@comment-4091815-20160203230230

There is no indication that it's a trait of the "Hale lineage."

So far, only three werewolves have been able to fully shift on the show. They all happen to be Hales, but, according to all characters who've discussed it, the ability is rare. We also saw how difficult it was for Derek to get to that point.

Canonically, it is a rare ability among werewolves and is not automatically hereditary.

There are several possibilities when dealing with a chimera. They don't really have much to do with the canon of genuine creatures on the show.

The key point Theo made was that he could show Malia how to fully transform meaning he knows she can do it too.

Considering how difficult it's been shown to be for werewolves to fully transform and the fact that Malia did it easily as a child added to this casual offer of assistance from Theo suggests strongly that it's not as difficult for Malia as a werecoyote.