What is the walkway made of? It can be difficult to train dogs to go on a specific surface since they have their preferences. Me, I'd let them have a patch of grass if that's what they prefer. Otherwise, you may start seeing problems with the little female holding it until she gets back into the house.

It's made of pea gravel, which she has pottied on before. They don't mind the surface; they're on it all the time.

I do let her go in the yard after our time on the potty patch, so I don't make her go straight back into the house if she doesn't go.

It seems like they understand the word "potty," so I don't understand why Chloe is being stubborn about waiting until she's back in the yard to go. I may just need to work with them more consistently. Problem is, I take the time (sporadically so far, I'll admit) to train first thing in the morning, but the rest of the day, they have full access to the yard. Unfortunately, the yard is between their doggy door and the potty patch.

You know the answer, keep up the god work, be patient and she will get it. Good Luck

Should read good work, not god work, but whatever works :-)