Welcome to Yorkie Talk and congratulations on the new addition to your life! You will have to share some pictures of Bella.
Here is a video tutorial if you need help with photos:
http://www.yorkietalk.com/forums/my-...orkietalk.html
I do not believe that dogs pee where they shouldn't to act out. Make sure her pad is readily accessible and that she doesn't have to travel far to get to it. I would limit her freedom to a smallish area with the pad (one room?) until she improves.
Be sure to praise and reward when she gets it right. My boys are 4 and 5 and we still praise them for using the pad. It's a sport in our home. They dash to the kitchen for their kibble reward. Teddy does the kicking dance when we cheer for him.
When she has an accident, don't make a big deal. Maybe say "uh oh" and show her the pad. Then clean thoroughly to remove the scent that may attract her to return and mark the spot again.