Dog that chases reflective light spots for hours?

Since spring weather has brought out the sunshine and with it alot of shadows and light spots our 1 and a half year old collie/aussie mix that we adopted in december has been crazy chasins that she cannot catch. She will drool, prance in circles, pounce on them, and totally ignore us just to play with these spots. She goes crazy when I try to do the dishes because the water reflects on the ceiling and she can't get to it. How can I desensitize her to this?