Introducing a new dog to the pack

This time I'm writing in hopes that someone has some good advice.

I wrote you about our new "family member" Freckles. She lives with my neighbor a mile down the road. He'd love to bring her along when he comes to visit, and I've always taken my dogs along when I stop by to see him - but one of my dogs is being a complete pill.

She takes serious offense at that puppy rushing up to say hello, and the other day I was actually afraid that she'd hurt the pup, so I hurried and got her back in the truck.

I don't know if this is a jealousy thing, because she always got lots of attention from this neighbor, or if it's just because the puppy is so enthusiastic. When we did obedience classes there were only 2 dogs out of about 50 that she didn't like - so her normal behavior is to be friendly.

Any good ideas?