I started having the same problem with Lady recently. The Ebayer I was getting pads from stopped carrying them and everything I have gotten since has been really thin and not as absorbent. I guess Lady didn't like to get her feet wet so she started going right on the edge of the pad!
I got a roll of Pish Pads and cut them to size to put underneath. These things are fantastic! They absorb all the spillover quickly. They are amazingly easy to wash, too, which was my biggest concern.
http://www.pishpad.com/