Is my Cat's leg broken?

Most animals hold their leg up like you describe if its been hurt. Cats are clever creatures when it comes to injuries and seem to know instinctively to lie down and rest the limb. If she managed to get home and into her bed it's a good possibility that her leg is sprained but you are doing the right thing by taking her to the vets tomorrow. She hasn't reached the age of 15 without a scrap or two! Glad to hear she ate her dinner. Try not to worry too much......although you probably will because she's your pet and you love her. Good luck at the vets. Keep us posted about how you get on. xxx