How to help a dying African violet?

My daughter gave me her African violet plant in 2007. It was puny and dried-up looking and had never bloomed for her. I repotted it and placed it in my kitchen behind the corner sink where it gets indirect light. Since then it grew into a large, healthy plant that bloomed almost continually. Just since December, though, it wilted and looks matted down, stopped blooming and looks like it is dying. I gave it some African violet fertilizer and put some new potting soil around the top where it was getting skimpy. It still looks terrible. Do African voilets die of old age? What can I do?