I suggest, now that you have read some reviews, Googling the issue; you will be deluged with impressions, experiences, etc. A quick search here at LuLa will turn up many references as well. In a nutshell, the problem appears only in a narrow shutter-speed range, say from around 1/50th through 1/120th -- and that's only in the a7r. The a7 has a different shutter mechanism that's virtually immune from the shaking.
Unless 36 MP is crucial, why not consider the 24 MP a7 for your wife? I have both cameras and am hard-pressed to notice the difference when printing @ 16x20.
Good luck!
Ron