I think patience is the key here. How old is your girl? Yorkies all have really small bladders especially those in the young puppy stage. My Rusty is 12 weeks old and can hold for 8 hours without having to relieve himself, but he has had a share of a few accidents in his crate during the 4 weeks I've had him for. 1 time he peed in his crate because I think it was due to his new living environment (wk 8). Ever since then, he has kept his crate clean! Don't forget to wash the crate.. Eliminating the mess and odor is a must otherwise Bella will be relieving herself again and again.
Before Rusty sleeps, I usually take the water bowl away from him 1-1.5hrs before he needs to go to sleep. This will minimize his water intake and will help maintain that bladder size to a minimum. However, I do feed him a few kibbles right before he sleeps just to make sure he doesn't get hypoglycemia while I'm knocked out on my own bed.
I'm a guy who just turned 23 so you might want to wait for the more experienced yorkie owners/breeders to chime in. They've always helped me when I was in need. A helpful YT bunch
CK