She is 2 years old. She was very good about going outside to do her peeing/pooing and has recently started doing it inside. What do I do

Is she healthy? Has she see a Vet recently? Has there been some sort of change in your household that upsets her?

It is also very important to properly clean where ever she has pooped and peed. Dogs are usually attracted back to the same area by the smell. You can buy specialized cleaners for eliminating these odors. You can also clean the area with vinegar and baking soda. The vinegar stinks at first but the smell goes away when it dries. If it is on carpet, you need to apply the vinegar and then blot it with paper towels or an old towel to pull the urine and smells out of the carpet. After it dries, check to see if any urine or fecal smell remains. It it does treat again with the vinegar.