Take her out about 15-30 minutes after each meal, and every 4 hours as well. Leave a poop sitting in back yard to remind her. Keep her on leash in back yard till she goes. Try to teach her to go to door when she needs to go- another dog who does that may be helpful to teach her. Keep an eye out for signals that she wants to poo, eg. circling around. If her poo is runny try giving her some canned pumpkin ( not the kind for cake filling ). If all else fails confine her to a smaller area of house that is tiled till she gets it.
Not sure her age, but if she's old enough to be fed twice daily vary the evening dose till you get a routine that works, eg. 8 am and 6 pm.
