When is a photo no longer a photo but a painting?

I created this image starting from a photograph I took of six bride's maids dressed in colorful dresses getting ready for a wedding. It was a lovely photo to begin with, but I wanted to experiment with the qualities of the colors and obscure the naturalism quite significantly to make it more impressionistic. I applied a generous amount of manipulation in Photoshop using the Art History Brush tool, and this is what I settled on as my final result. The feeling of using the Art History Brush on a blank layer which is superimposed over the original image is really very much like painting with a brush on a blank canvas. Though I'm not adept at using real brushes and paint, I am learning to reproduce a similar effect in Photoshop. So my question is this: when does a photo cease being a photo and become a painting? This looks more like a painting to me than it does like a photo. Of course it's not a "real" painting, it's a digital one. But I still think it's a painting. However, it's also a photo, since all the colors came originally from an image made on a camera. The texture and a certain degree of where the boundaries fall between color patches come from my brush strokes.