Why Are Shar-peis So Mean?

I have a lilac chinese shar-pei. She is the sweetest thing to be around when it comes to people. A little energetic, but real sweet. It's a different story when she's around other dogs. She growls and barks all the time, mostly at big dogs. I'm guessing it has something to do with the fact that she wasn't ALWAYS around other dogs or that my neighbor's lab always tried to bite her when she was a puppy. What up ya'll?