I truly feel for you. You have to get your head and Heart around the concept that you are providing "Hospice care at home" for her right now. I know realising that won't make it any easier in many ways, and won't take away any discomforts she is feeling, but it might help you to accept.
Acceptance can help because it becomes not so much about fear, as about "what is the next move I need to make, with compassion and love"?
If she still has decent life quality despite her decline, then it's good to pace things alongside her, but watch carefully for any sudden changes, or any sense you get that she is enduring on-going pain just because she wants to hang on.
Your vet sounds sensitive and intelligent. Does your girl have all the palliative treatments prescribed, which may make her last weeks/ days more comfortable?
That would be sub-q fluids, perhaps an anti-nausea medication, and painkillers, apart from any others which might be needed for additional symptoms such as diarrhea or constipation. Remember, narcotic analgesics -which work as well for dogs in terminal illness as humans -are constipating.
My heart goes out to you and your dear dog. Keep a close eye on her. Things can change at any time and decisions can 'turn on a dime' as the saying goes.
Bless her Soul, and she has someone who loves her very much....YOU.