Board Thread:Legitimate Canon Questions/@comment-13895380-20150813173930/@comment-4091815-20150813205712

Malia explained in Echo House that she didn't know how she shifted in the first place and had no idea how to get back to that shift.

She spent the time between Season 3 and Season 4 relearning how to even partially shift on command.

On the full moon she was struggling not to shift and managed to only go part way.

She has no idea how she did it the first time and can't replicate it now.