The thing is, she isn't so much a "good" character as just a very selfish one. I think there are indications that she's going to flip sides, but mainly because she's realising that her life as "The Commander's Wife" isn't really great and she's actually just as much a slave to it as the Handmaids or the cook. They kind of showed that in that episode. Yes, the handmaids etc. have been brutalised and the wives aren't... but, that's only if they don't step out of line. If they do, they'll be beaten and abused like anyone else. They also showed that wives can be sent to the colonies as well in a previous episode. But yeah... basically, she used to "be someone" and she wants that back, and that's why she'll end up turning on the Commander. She also doesn't LIKE mistreating people, but will turn nasty in a second if something gets in the way of her own best interests. TBH she's one of the more interesting characters in the show because of the nuance (along with Aunt Lydia who I mentioned before)