Mark, wow, very sorry to hear this.... unfortunately, I know very much how that can be when my partner's beagle had to be put to sleep due to an aggressive cancer back in January. He was my Christmas gift to him at Christmas, 2000.
I hope it is something else and she can be returned to your warm care in no time.
If not, celebrate with her, knowing how much she has given to your life and you have given to her. Remember, nothing is forever, we all have to face this stuff when we aren't prepared. Thoughts & prayers!