Hi M.,
Your daughter is starting to experiment with cause and effect. As others have said, this is a phase and it will pass! In the meantime, invest in some good bibs, get a large, easy to clean splat mat to put under her high chair, and keep dry clean only things out of spitting range! You might consider wearing a smock or apron during feeding time, too.
If you really feel that you don't want to outlast the normal course of the stage, you can end mealtime as soon as she starts spraying, along with a firm "If the food does not stay in your mouth, then breakfast/lunch/dinner is over. That also teaches cause and effect! Truth be told, though, I didn't have the heart to do this with my kids at that age. As I recall, the behavior only lasted a couple of weeks, until they established that the response of the feeder was usually pretty much the same. They generally repeated it if they were being fed by someone new, just to see what their reaction was.
BTW, I hightly recommend two books for you: "Games Babies Play" and "Games Toddlers Play." These books address different developmental stages and the way that kids approach them and learn through their play.
Have fun -- they do grow up so fast! I can still very vividly remember my 9 mo old son spitting spinach all over our 4 year old niece. He just finished his first year of college, and she's starting Med School!