That's a funny thing to get hung up on, though I can understand it. I suppose that's the downside of some programming languages going with the worst assignment operator. If they didn't they could use = for (numerical) equality tests. If your wife has a strong mathematical background you could also show her some logic programming like Prolog or Mercury.

Also, various ways of assignment:

Pascal style:

  x := x + 1

Scheme:

  (set! x (+ x 1))

Forth:

  x 1 + x !