Is there any reason why the dog cannot go outside? Any dog of any age or size can learn to hold it for a reasonable period and eliminate outdoors.
It's a pretty common problem I think, and it's because pups learn to eliminate in connection with a substrate, which means they seek that out when they feel the need and also, being ON or near that surface stimulates them to go.
What can happen is, the pads (or newspaper) are on a surface like tiles, and the dog connects weeing with tiles as well as the pads. Perhaps, a couple of times, the dog is desperate and so isn't QUITE on the pads when she goes, or is just within sight of them.... or even the brand has changed how they make the pads and they no longer feel "right" to pee on. Before you know it, tiles have become an Ok surface to eliminate on, or even a new, preferred one.
Are you putting newspaper under and around the pads, to make the clean up job easier? It may also prevent her from making the association that the floor is the right place substrate to eliminate on, and may even help if you run out of pads in future, or if they change the material again.... at least newspaper remains pretty constant 
Unless you can find a brand of pad that she "likes" soon, she's just
going to be accustomed to peeing on tiles, and finding a "good brand"
won't make a lot of difference; she will already have got into the habit
of peeing on the floor. With this in mind, it would be far better to
take her outside frequently and give her a tasty treat and lots of
praise if she goes out there. It should also save money on pads in the
long term.
"Give a man a fire and he is warm for a day, but set fire to him and he is warm for the rest of his life." - Pratchett, "Jingo"
