Women tend to pick balls that are too light for them.  Most women can throw heavier then they are willing to try.  Keep in mind that if she's using a house ball, she can go up in weight with a ball drilled to fit her.  It will be easier to hold onto.  So if she's using a 10lb house ball, try 12lb purchased ball.  

I think some of the most frustration for wives is that their balls deflect so much that they don't have much chance at striking.  Especially if you, their hubby, is striking like crazy.  They won't understand why their ball doesn't do what yours does.  And ball weight it a big contributor.  I'm not saying jump into a 15lb ball, but most women can handle 14 if they are a normal healthy lady.  

I too do not suggest jumping into anything stronger then a Noize or Razor, maybe a Bash. If she sticks with bowling she'll want an upgrade rather quickly.  But something of that level and down will be good enough if she's just out there keeping you company.  

Erin