I think it is a good thing that even though she hides her depression, she at least acknoledges it as evidenced by the fact that she has seen a doctor and has some medications.

Does she have therapy too? I believe that medicines are only a part of the answer, and therapy is just as important, even for learning ways to cope with the illness.

If she doesn't like the way the medicines make her feel she should talk to a doctor about changing prescriptions. It can take a very long time, since each medicine takes several weeks to see if it is working or not, but many people can find the right combination that works for them and doesn't effect the way they feel negatively.

As for the codependency group... I really don't know the proper etiquette and protocol for that, but my guess is that it would be OK to talk about your wife's problem. I would think that the group would be held to strict privacy, just as any support group would be, and that in order to really help you it would be important to be able to speak freely about the problem.

I do think though that it is important that you be comfortable talking about the problem and I am glad that you respect your wife's privacy. I would bring up the question at the group, I'm sure this is an issue for everyone there, see what their policy and advice is about sharing the nature of their spouse's ailments, and then think on that and see if you can become comfortable talking about it.