Board Thread:Rewatching "Merlin" - Season Four/@comment-5102537-20131229110740/@comment-5674726-20140111234015

Fimber wrote: This is one of the many episodes that made me wonder why Morgana never considered Emrys to be a potential ally and someone who has good reasons to protect Arthur.

I'd say that, once she was told that he was her doom, she took the view that anybody who wasn't with her was her enemy. I doubt that she'd have considered that there could ever be a valid reason for a sorcerer to support Arthur, as I don't think that she believed that he would ever change the laws against magic - and, in fairness, she was right about that.