It really depends on how large your apt is and how many floors but I like the previous poster feel it is hard to change. I would be sure to take one or two with you when you move that your yorkie has peed on and put that down and stay close for awhile until Lexi does pee and then go to the next area you have a pad down. I moved mine once and moved it about 2 inches a day until I got it where I wanted it.
They get set in their ways but also they are very smart and with a little reward once in awhile for doing it right she'll catch on I'm sure.
I never litter trained a dog but many have. I do think that would be easier in a pup rather than one that is used to pee pads but I could be wrong. Someone here will surely give you ideas on it if they haven't already. I always used a flannel back plastic tablecloth under each pad (cut is up in 1/4's)