My first suggestion would be to determining how your wife views herself. She may not see her symptoms as being problematic or identify herself as being depressed. Even though the symptoms you described seem pretty straightforward, her impressions may be different. If there are other family members, friends, or even family doctor involved it would be to your advantage to solicit their help in addressing this issue. Furthermore, the timing and manner you bring up your concern could be a factor in her motivation to address her depression. If your asking her to seek out medication in the midst of a depressive episode, she may be resistant to your suggestions.

I would suggest bringing up talk therapy to her. That may be less threatening for her. If she engages with a therapist that may offer a better transition to medication, if it is indicated. if she is still reluctant in following through with this, a less threatening starting point may be marital counseling. If you present this as a couple challenge, she may be more open to working on it. If your wife is still resistant, another option would be seeking out professional help yourself. There are individuals who specialize in interventions and would be able to assist you in confronting your wife in a productive way.