I am no lawyer and this is not legal advice, however, if it were me, i would find a general lawyer that seemed a bit trustworthy and explain the basics and ask for advice for a specialty lawyer as a referral. A small law office could probably refer you adequately. Either way, your friend's wife will need the lawyer if only to fend off any advances toward taking the property. Once the company knows they have to go through a lawyer, they will realize this will not be easy.
Also, and this is only my opinion, the company has copies of all designs, at least in paper form, so they are after the source files to continue or improve. This must be worth something to them, although not millions, but perhaps tens of thousands. As someone else pointed out, if you or someone else close to the widow separated and copied all of these files, it could be worth a few thousand dollars to the company for you to do so, if the widow agrees, or is forced to give them the source files. They can't just barge in and take stuff. As theses things go, however, it is best to act quickly.
Either way it goes, the widow needs a lawyer and it is good that you are helping her, however, you need to realize your boundaries in this matter. It is easy to get emotionally involved and start making decisions for the widow that perhaps is not in her best interests from her perspective (not yours).
Good luck with this.
As always, this is my 2 cents...