I did much the same for my brother, a non-runner.
In general terms, I made it far more like a marathon training programme - on the basis that the time he (and your wife) was likely to be running for was nearer to a competitive runner's marathon time than to a competitive runner's half time. The important thing I thought was to build up a long run to 10/11 miles in the same way as you would build to 22-23 in marathon preparation. Don't underestimate that she may be concerned about being able to cover the distance without blowing up in the same way as I was concerned with my first marathon.
I also went easy on the rep sessions and got him to do things on perceived effort. i.e. I'd suggest he ran either at, quicker than or slower than race pace for whatever lengths of time.
Much less complex than the marathon training I was doing at the same time, and also much less pressure - no pressure to hit times or fixed paces (partly, I admit, because I had very little idea what to suggest paces should be as he had no race times to work at). If you set a session which she is doing on her own and she is struggling to hit times she is going to get demoralised pretty quickly.
In the end he ran a hilly half on a hot day in (from memory) 2 hours 3 mins. Maybe he could have gone quicker if we had done a more pressured and structured programme, but the point was he didn't hate the training, got round without blowing up and was pleased with his achievement.