I've talked about this story a number of times, but very early in my diving careeer (days after getting OW) my dive buddy got hung up on a wreck, in a deep dark passage, had her reg ripped out, and couldn't find her octo. I and the DM were in front, so didn't see the incident. Mel admits that she paniced, and would have shot to the surface, if not for the fact that simply wasn't possible. Eventually she found her octo, tooks some breaths, coughed the water out of her lungs, and lived to tell the tale.
I spent the next dozen or so dives frustrated with her wondering why she couldn't seem to relax and enjoy it.
Fast forward to two weeks ago, I had my own incident underwater (posted in this forum). I went for another dive that very afternoon in a deliberate attempt to get back on the horse, but spent the next 10 or so dives, VERY uncomfortable underwater, not enjoying it at all. I can now sympathise with Mel, and your wife, in a way I didn't understand previously.
My point is, take it slowly, slowly try to re-introduce your wife to the joys of diving, and at no point ever push her. Maybe go on some super pretty, super shallow dives to build up the confidence. I also have had a LOT of problems with my regs of late (not due to the regs per se, but the stupid tech who last serviced them) so ignore the fact that the tech tells you that they are all fine - there is no test apart from using them at depth, and techs vary in ability and experience. If your wife wants new regs, and you want her to keep diving, buy them. But just be aware that reg issues are going to happen -in fact are almost guaranteed to happen about 20-30 dives post every service as the seats bed it. What you need to do is build condfidence to a level whereby such an issue simply becomes an annoyance, not an event to promote panic.
My personal advice (crap though it might be) would be to tee up some dives with a good instructor to refresh those skills that might have been glossed over during the OW course. Do some OOA drills, some buddy breathing, some mask clears etc. The point being to get to the point where your and your wifes level of comfort underwater reaches the place where issue become simply things things to deal with, not things to panic about. As they say, stop, breath, think, act. Hell, on my OW course i almost panicked every time I had to take my reg out, now, after only a trivial number of dives, i've had people offer my their alternate because i was sitting there with my reg out for an extended period of time for some reason (such as when I was sitting their rubbing my sore gums after the rental reg cut them up). The point being, practice really does lead to comfort, which leads to an ability to not panic at the slightest issue.
As an avid reader of the accident forum here, it seems that panic is by far the largest and most dangerous thing to deal with underwater, almost everything else is solveable as long as you have the right training and buddy. For me, both GUE and Rescue training have put in me a faith that no matter what, if I am diving with people I know and trust, anything is solveable, as long as we all remain calm, think, and deal with it.