This is such a heartbreaking disease. I'm so sorry to hear about this. I don't know if there's much you can do to prepare for it, but it might help in knowing that Lymphoma can be very, very aggressive in dogs. At least it was in my experience that my mom also described above. It's shocking to see how fast the disease moves. When she started showing signs of low energy, one thing that seemed to help a bit was DMSO (given orally with a dropper and diluted). That will only do so much though. Sadie had very rapid weight and muscle loss at the end. Once you see that progressing, I think it's the humane thing to lay her to rest. I agree with Laura that the best thing your family can do it would be to share the love they have for her in the remaining time. Again, I'm so sorry to hear this.