Hey, I get that it is frustrating. I am looking at things that you might do differently -- not to make you feel bad, but hopefully to give you a new approach. I did not have as tough a time as you did with my yorkie, but there was a while where I thought I would he would never get it. I even started a thread, "Untrainable?". As I mentioned, there were times when I was watching Thor with one eye, and he would still fool me. Once, I was even on YT, complaining about his potty training, and while I was typing (and watching him), he peed on a rug!
About the UTIs, I just meant that maybe it's taking her longer because she hasn't always had full control over her bladder. It can take them a long time. After my experience, I think it is genuinely difficult for some yorkies to grasp what is expected. Their potty training is our differential calculus. I sometimes felt like Thor was just trying to drive me bananas, but I realize that he is just not that smart (though wonderful anyway). He LOVED his potty treats, so I knew he was doing his best, but his best still meant little puddles on the floor.
Given that you paid so much for this trainer, can s/he come to your house and review what you are doing? Maybe it's something small.
I use specially scented pads (also Nature's Miracle) and am very happy with them. However, I live in an apartment, so it's more of a challenge to get a dog with a small bladder outside.
Has your girl ever gone even a few days without an accident in the house? Once you get a few days going, even if they have an accident, it means they are getting it. It is extra tough when they potty in their crates. I haven't seen a good solution for that except to take them out frequently enough that they get used to a clean kennel.
Hang in there.
