Just wanted to pop back in and say we are 11 days errorless!
I switched her to the Flexi and it's made a big difference. I think being able to run around and get things moving is making it much easier for her to go, or at least it makes her need to go sooner! I haven't needed to stay out for 15 minutes, and there has been a couple times where she goes within a minute or two of going outside. I've been making sure to walk her around after she goes, because I don't want her to figure out that going poop = back inside. That would be great if it were winter, but it's actually been nice here.
One thing I have noticed is that when she has looser stool (not even soft serve texture, just a slightly bit more loose) she will completely expel everything, but when it's firm, she won't. I'm considering keeping her on a food where she has a slightly looser stool, because I'm starting to think that she is just having a hard time pushing out the firm stool. We'll do bones a couple times a week to make sure her anal glands get expressed, but at least for now, it will make the housetraining easier if she is emptying herself.