Gosh Dixie - this is a hard thing to do, but I think you'll be doing the right thing by having her spayed in the long run. My female Chihuahua will be getting spayed in a couple months and I even have mixed emotions about that - but I definately don't want her to have puppies, I just don't like the idea of having her tummy cut.
Maybe you can take a trip to the shelter once in a while, hold and smell the puppies to get your puppy breath fix