Rosemary Christmas Tree?

Since I have a small apartment, I've resolved to buying a small Rosemary Christmas tree for the past two years. It's about 18 inches high and 8-10 inches around at it's base. This year, just as last my tree is dying. I've read articles that say that they need regular watering and good drainage and I thought that's what I did. This year I even transplanted it into one of those pots that have a lip near the bottom instead of keeping it in the original pot with just the holes in the bottom. I'm also watering it once every day with about 1/2 to 1 cup of water. The "dying" starts near the bottom or on the side of the plant and works it's way up to the top. The top part really looks healthy, but everything else is completely dried out. What am I doing wrong? Am I over watering it?