So sorry to hear this, Phil.
Holly is the luckiest of pups to have you and Ruth to make every day for her the best it can be. No pain, and no fear - that is a good combination that is perhaps the best that any of us could ever wish for. May she have as many days as possible just like that, with as many sniffs and treats as she can fit in.
All our love for this chapter, hard and sad though it is.