A friend of mine had to let her Corgi go back in June, he was 15. Her other Corgi, who is 4, had been with her brother all of her life.
Just tonight I asked her how Tucker was doing since losing Cowboy. She said she is finally coming around and is playing with the cat a lot more these days.
So it does take a while for them to get used to life without the other. But as others said, keep the rountine the same and she will eventually come around. I think your son coming with his puppy will help distract her for a time.

Have a good holiday and please give Annie some hugs from me too. And I'm sorry for your loss of Princess.