Bond funds can help you diversify and reinvest dividends. They offer access to debt securities otherwise unaffordable to small investors. They do tend to provide income. She got a fixed amount of income every year and recovered her principal when the bond matured. When you invest in a bond fund, there is no certainty that you'll get either.
Bond funds can be brutal.
When you buy an investment-grade bond and hold to maturity, you're buying into stability. When you purchase a bond mutual fund, you're buying into the bond market. That's anything but stable. The variety of bond funds is vast. There are municipal funds, bond-index funds and funds that mix and match from many categories.