This was a few years ago, but my mother walked away without a scratch after a head on crash in a MB 300d (wagon). Her opposite number was a suburban.
What was she hit by? Honestly, everytime my wife backs out of the garage, she realizes how small the 3 is compared to our truck (2011 F350). It's easy to see how someone might feel....unsafe?...in a vehicle that small.
She is getting help, which is the most important thing. Do you need your truck (work, hauling stuff, towing stuff, etc)? Can you sell it and take over your wife's car and get her another V? Would she feel better in a bigger vehicle, or is it just that the V is what she felt safe in?
It may be an expense, but give your wife what she needs. From my own observations and experiences, helping your wife get back to normal will be cheaper in the long run, and easier on everyone involved.
Finally, have you considered that even if you get a new V, she still might not feel safe? I would consider renting one for a few days (maybe just a regular CTS) and see if she's ok with it, or if she might want something even bigger.
Good luck to the both of you, and best wishes for her quick and complete recovery.
2013 BMW 550i M-Sport - ZCW, ZDH, ZEC, ZMP, 2TB
2011 Ford F350 Crew Cab Short bed
2006 BMW 330i Premium, Sport, Automatic, Comfort Access
2004 Lexus GS 430, 2001 GMC Yukon, 1999 Pontiac Grand Prix GTP, 1997 Ford Thunderbird V-8