My dog hates the heat, actually seems debilitated by it. She's in a/c most of the time, has plenty of water, and exercises in the evenings by running around under the hose, but I always wonder if I should clip her fur. She's a collie mix, and has a pretty thick coat (not long but pretty shaggy). I've always heard that the fur insulates them, and they actually suffer more if you cut it. True, or should I give her a trim?