It depends on a LOT of variables. How much time per day does she spend quilting. How experienced she is. How complicated/dense the quilt pattern is. How big the quilt is. These are all factors that can add to the amount of time it will take.
I would keep in contact with her, just keep sweetly asking about the progress of your quilt, and let her know you're excited because it's your first. I'm a little bothered by the fact that she told you 4 weeks, but at the 4 week mark she still has 3 quilts ahead of yours.