Originally Posted by Bundybear
Perhaps you should do following:
Have her leashed at all times. Meaning - attach the leash to your belt and let her go wherever you go around the house. That way you can predict when she needs to go. So take her out for toilet breaks every 2-3 hours for start to a designated spot. When she does her business regardless of no. 1 or no. 2 praise her excitedly and award with extra yummy treats, then go inside and do whatever you do around the house. But make sure she is attached to you all the time without exception. If you're not able to, your fiance can take over. After a while unwanted behaviour will fade away, but it won't happen in one day. Try it for a week for starters. Even when you go to bed, have her leashed next to your bed and give her a toy for entertainment. You can use stuffed kong or something similar. She won't be able to do her business when she wants and where she wants, and if she wants I guess grown up dog will let you know. In time you an extend time between toilet breaks.
Also, just in case it is attention seeking - how much actual time do you guys spend interacting with her? Playing, doing stuff i.e. little obedience etc.? I asume she does get a lot of excercise if she's around horses etc. but sometimes just running around isn't enough. A dog needs interaction and since she is a working breed she needs some work to be happy.
edit: I see now others have suggested the same cheers!
Respect and you shall be respected. Animal is always right.