Paulus, I can tell from your post you really love your wife and want to do what is best for her and your relationship.  Can't her new doctor give injections instead of pills?  Have you asked him?  If she was lucky enough to find something that worked before, it is my opinion that she needs to return to that same treatment.

If injections can't be given, then she needs to work with her doctor to find a pill that will help.  There are many different antidepressants.  I had to try several before finding one that worked.  And actually, I now take two different antidepressants every day to feel my best.  If one medication has not worked over a period of months, it is time to try a different one.  But if I were you, I would try to find a doctor will give the injections.