Hmmm. In the last panel... is it Wanda going "Eyuh"? I wonder why she doesn't want Oss calling her mistress. She doesn't seem to mind it from Ansom.
I haven't read all seven pages of responses yet, did someone else address this? As far as my reading goes, it appeared to me that Ossomer just called her mistress -- something that seems to come automatically to the decrypted. But he's still having a hard time adjusting to being decrypted and grunts out a personal distaste for the title -- "Eyuh." Wanda realizes the conflict and remedies the situation by removing the conflict, allowing him to call her by the title of commander and not have to deal with the personal relationship aspects that come up with a word like mistress.
Notice that the speech bubbles are coming from two different places. It's too small to make out any distinct figures they are pointing to, and it's possible that they are both pointing to Wanda, but I think it's more likely they are not. If this is the case, it gives us further insight into how Ossomer is taking his decryption and the variety of ways that units respond to it.
Perhaps the difference between Ossomer's and Ansom's decryption experiences was that Ansom assumed he was going to be dead, gone forever, and suddenly found himself re-popped by a mysterious and grand magical force he never thought possible, by a caster he didn't know too well. Ossomer was well aware that he would be decrypted when he died, and would have preferred to stay dead. He had intense and personal hatred for Wanda, considering her an evil witch. Ansom had no such feelings to overcome, but Ossomer still holds some of those negative feelings even though they are suddenly secondary to loyally following at her side.