Why has my dog stopped drinking water?

I have a 2yr old Yellow Lab - she is healthy and UTD on all her shots. She has never been a big eater or drinker but lately she is barely drinking anything at all. I have not changed her bowls or the water I am giving her and I have made sure her bowls are clean and free of any debris. She has one bowl downstairs, another bowl upstairs, one outside and has access to fresh water in all bowls daily. I don't understand why she has stopped drinking and I am starting to get worried. She is still very active and is acting normal but where I live it has been really hot for the last few weeks and I know she needs to be drinking. I have even tried putting fresh cold water in the bowls a few times a day instead of just once but that didn't work either. She used to come running when she heard me filling any of the bowls now she doesn't seem to care. I have also tried giving her ice cubes and putting ice in the water but that doesn't work either. I know I can give her chicken broth or something but I'm afraid if I do that, that's going to be the only thing she will want. How can I get her to drink water again? Please Help!