Size Doesn't Matter

We recently got a puppy. A papillion. For those who don't know what that is, it's a lap dog. I didn't know what it was either.
Well she weighs less than 10 lbs right now. When I take her outside she insists on trying to chase cars. Each time a car goes by she perks her ears up and runs to the end of her leash.
I'm like, what are you going to do if you catch one? Wrap your teeth around the bumper and hang on for dear life?
Plus she barks like she's a big dog. Our neighbor's dog was outside the other day (he can knock down a grown man) and it started barking at our puppy. She stands up and just started yapping right back, like 'bring it on big boy'. I was almost rolling on the ground.