In his autobiography "Will" G. Gordon Liddy (remaining a convicted felon for his involvement in the Watergate burglary) wrote that his wife maintained a good collection of firearms, some of which she chose to keep on his side of the bed. Amusing anecdote at best. I'm sure that any number of prosecutors would love to take another shot at Mr. Liddy.
A really simple solution might be a biometric gun safe programmed to be accessible only to the lawful owner of the firearm and mounted securely to a floor, wall, etc, in the home. It would be extremely difficult for a prosecutor to prove constructive possession by the woman in question.
With so much public fuss about gun control, and so many political irons in the fire (yes, in California also), it would not surprise me if authorities tried to make a case in a situation like this. I would make every possible effort to clearly demonstrate that not only was there no reasonable access to firearms, but that there was a clearly understood agreement denying her any access whatsoever. Perhaps a written agreement signed by both parties, witnessed, notarized.
