Try to get her on a regular pooping schedule by feeding her at the same times everyday and no other time.
Also, if she is doing this at night, crate her for sleeping. In the morning, let her out first thing, and then again about 30 min later. After that, every two to four hours.
It will take some time re-training her to go outside, but stick with your schedule even when it doesn't seem like it's working. It could take 6 months!
Good luck!
Oh, and don't forget to praise like crazy when she goes in the right place.
__________________
XOXO Melissa and the Tooties |