Why would my warden not trust Morrigan? After all she helped him/her recover from his wounds,fought along side of him/her,my male warden has romanced her early in the game and Morrigan will save my warden's life by doing a ritual.
First Flemeth helped your Warden,not Morrigan,second i didn't romanced her so my point of view is neutral and not polluted by personal affection..
Is not a matter of trust,or at least it wasn't for my Warden,it was a matter of goal,i don't care if she intended to save my life (which i can do without her) save the old god was not an option,these things cause blights when are corrupted,as a general and devoted Warden i cannot gamble the security of Thedas for my selfish interest,as i said my Warden valued the safety and security of others more than his life.
I refused this plan popped at the last moment and she abandoned/deserted the army, is morphed as heavy betrayal from a militaristic point of view,especially because she leave because she doesn't get what she wanted,which is something completely unreasonable into an army,soldiers/volunteer who leave the general because of their personal interest(yes the Warden is a general at redclieffe not a soldier).
Is the same in Dragon age Inquisition,if Morrigan would have abandoned the Inquisitor and his cause because she doesn't get the well of sorow,it would have been considered as betrayal ,but she didn't this time.
As i said it was a matter of goals and you don't need to sign contract,since that you have decided to willingly follow me and my order only to desert later.IS desertion/betrayal when the DR is refused it doesn't morph in something else just because she was a friend or a lover.