Your problem is that your doggie has a shorter tail and a smooth coat. I have used female doggie diapers with a sanitary pad for my female Scottie a few times due to some medical issues. They worked great if she was shaggy. When she was freshly groomed, she would walk out of them. You can get a washable diaper that you can use sanitary pads in.
http://www.drsfostersmith.com/product/prod_display.cfm?c=3307+32+14459&pcatid=14459
You might be able to get a better fit around the tummy with this. Since it is fabric you could even alter it slightly to get a better fit.
Even with this, you might want to get a waterproof pad for her to lay on in the bed. We keep a baby crib pad or changing pad on the floor at night--just in case. These are washable and have a soft fuzzy feel on the top so your dog would be more comfortable. We like the size of the unfitted crib pad better than the changing pads due to the size. Any urine soaked items get a rinse in the tub and then washed with vinegar and enzymatic cleaner. If she is losing bladder control at a certain time, maybe you could set the alarm and give her a quick walk halfway through the night (I know this will get old quick though).
I'm sorry your baby is sick. I hope you find a good solution to her incontinence problems and you can have many more happy days together.