Jason .......
I'm going to reach a little here ... and also state i have no medical training at all. It does sound to me like your wife may have a guilt complex. I say that because I had one myself for much of my life - that is, until I saw a psychologist for a good length of time.
Of course, she has depression and the med she was prescribed is one of the most common for depression. I take 20mg Lexapro myself daily. For me it helps - but everyone reacts slightly diferent to meds. It does soundlike she needs more than Lexapro - either in addition or as a replacement.
I would guess it was prescribed by a primary doctor .... and that's sort of like going to a psychologist or psychiatrist for checking your foot arch - or for the flu. It's the wrong type of doctor.
She does need to go see a talk therapist of some type. It sounds like she needs to find an outlet for releasing her anger. I'm sure she needs a person to confide in also - and don't take that personally! I mean a trained professional.
Some are better than others. Finding a good match would be worth spending some time to do so. BUT .... how do you get her there in the first place?
Hopefully, someone will come along with a good suggestion. My former wife would not go .... no matter what! Denial can be a very powerful and selfish thing!
Best wishes to you.
Rob & Gizmo