User blog comment:Morganaforever/Episode Review: With All My Heart/@comment-5465618-20121201212324/@comment-5674726-20121201215847

''I know! But hearing how Aithusa was MORGANA's dragon I expected things to be different with her.''

Aithusa may be with Morgana by choice but, as a Dragonlord, Merlin can still force her to obey his commands and since poor Aithusa can't speak, she can't even tell Morgana that she could be compelled to act against her.