Yorkies are notoriously hard to potty train. Patience, diligence and consistency are the best advice that I can offer. As much as you dislike confining her to use the pad, you must be dilegent in your training. They like routine and really if you give them mixed signals, they will get confused. When potty training, you should restrict their roaming abilities. Some have even suggested tethering them to you with a lease. We did this for a very short period of time with Maggie.
I personally didn't care to use a crate for potty training but did use an expen. I kept the pad, crate, toys, food and water in there. I would watch like a hawk and learned the signs that mine would give when they were going to potty and placed them on the pad, over and over again until they used it. When potty training, you should use one phrase for it and initially only say it when they are in the act of going. Once they associate this phrase, they will understand it when you take them for a walk.
Consistency is what you will need to keep at it. As for walking outdoors, mine get into rabbit poop, YUK! You will just need to try and keep an eye on what she gets into. Hot Rod took to the grass with no problems whereas Maggie would pee but not poop. She would literally come back in and head straight for the pad to poo. It took her a couple of months of praise and treats before she would go outside. Thankfully she has no accident and very good about using the pad. She is almost 4.
Now Hot Rod, my 4 1/2 year old has reverted to pooping in the house if he cannot go outside.
He pees on the pad all day long but would rather potty elsewhere. He gives definite signs of when he has too poop, sometimes he will run over to that pad but then kinda jack rabbits on the pad and runs off. We've gone back to training 101 and put the gates up to keep him in the kitchen/family room areas. It's worked to a point as he chooses to hold it most of the time til we take him out but I have found surprises from time to time if I forget to close the gate(s).
Fortunately he's pretty consistent in his schedule so it's pretty easy to take him out at those times and as a result no accidents in the house.
Just keep at it and it will happen. Patience, diligence and consistency! Good luck.