My Granddog is having troubles

My son left SC for NC because he was offered a job. He took my 6 yof granddog with him. He is living with friends who already have 4 dogs. The friend's dogs are a 6mof and a 5mom and two puppies, probably not much over 6 weeks old that they found wandering on the road.

My granddog Gwendolyn (who gets along fine with our cats btw) gets on fine with the little puppies. However she snaps at the older dogs, and they snap at her too. They are not at all friendly with each other.

Also Gwendolyn barks at every move the friends make. She'll accept treats from them, wagging her tail and growling at the same time. When they get off the couch to use the bathroom or get more treats, she barks like crazy at them.

It's only been two days, but my son is really afraid that this constant barking is going to wear thin soon.

Any ideas on what he can do to calm her down? She NEVER has growled at anyone in my house. She is truly a good dog. Stubborn, but a good dog.

TIA!

CarolinaBound!