Euthanasia Question - What About Companion Pets?

JEANNEMATSON asks: "Our sweet 12 year old dog, Friskie, has terminal cancer, so we are facing the decision to euthanize her. We have been through this ordeal before 8 years ago when Friskie's pal; Kelly had to be euthanized. All Friskie knew at that time was that her friend left the house and never came back. Friskie didn't eat normally for weeks. I'm wondering if it's a good idea to bring Friskie's pal, Sammie, with us to the vet when the time comes to say goodbye to our Friskie. Has anyone else ever done this? My thinking was that it might help Sammie to understand what has happened to her friend."
Related article: Euthanasia - How Will I know When It Is "Time"?