She has been sympathetic to Deliah, but sympathy has limits. In general sympathy tends to be given by those who have the leeway to do so. Deliah tried to get Myne enslaved (and effectively killed) even if she didn't know what she was doing it doesn't change things.
If someone tried to kill you and your family because they were brainwashed, would you have the leeway to be sympathetic? You may feel bad for them, but it doesn't change the fact that they tried to harm you.
End of the day, Myne has a right to be angry with her even if she sympathizes with her. And Delilah definitely owes Myne an apology. Doing wrong even if you were tricked doesn't excuse yourself from the wrong one committed.
