My dog refuses to go potty outside?

I have a three year old chihuahua named Bambi, and she refuses to go outside and use the bathroom, I have tried and she will go outside at my moms which has all wood floors, but at my house which is carpet she will just go inside and not even tell me she has to go. PLEASE HELP ! I JUST SHAMPOOED THE CARPET AND WANT TO KEEP IT NICE!