Not only a number of different stocks, but different types of investments. The reason is simple. Events that are bad for one type of investment will work to increase the value of others. Bad news for the stock market is often good news for bonds or real estate. No-load mutual funds are an excellent way to participate in each.
Diversification is great insurance for the average investor.
Starting Over should try to have about ten different investments. That way even if one loses money it won't impoverish her. Finally, a comment to anyone who's thinking of going down this path. Your marriage may be hurting you emotionally today, but a divorce could add financial pain later. The plain fact is that divorce is expensive.