For adult dogs I always took them out first thing in the morning, fed, then about a half hour after eating & until they did #2, again about mid day & then right before dinner & a half hour after. It worked great once they realized the schedule. But it also depends if they are drinking more often because of the weather or getting extra food/table scraps/treats. But if you look at it as logically what goes in must come out w/dogs usually about a half hour later & what do you have to do first thing when you get up & before you go to bed-pee
so its kind of a formula which can change when you add more to the equation.
keep offering the pads at your dads she may get comfortable enough to use them there.