DISCLAIMER: Since you posted very little info, I have to make assumptions.
I'm guessing she's not show quality because you would have asked your breeder that first. Since you didn't, and you are thinking about it, then that probably means that she's not from a reputable breeder. A responsible breeder would have spayed all the pet quality puppies. Because she's from that type of lines, chances are she'll pass on some sort of disorder, even though she might not show it, or there will be a complication durring pregnancy or birth, in which case you might loose all or some puppies, or even your precious bitch.
The tests to make sure she doesn't (as well as the sire) have any problems that might cause death/complications durring birth or pregnancy are very expensive. Plus C-sections and after birth care can get VERY expensive.
Additionally, letting your bitch come into heat increases the chance of reproduction-relacted cancer, which are also very high.
Finally, breeding dogs carelessly quickly leaves a trail of destruction that we then have to dedicate our time and money to save.
*Only breed if you have a goal in mind as to what you will make better, whether for show or work. (Not to many westies actually work going to ground nowadays)