I know this feeling. It sounds like you are preparing yourself for her final days but she is not ready yet (from what you describe). During these times of transition I sometimes hoped that the dog would just die, but merely to end my suffering. Then after a while I had come to accept that it was going to end in a few weeks or months and I was able to enjoy the last days with him/her again and the goodbye would be OK in love and not in anxiety. (except for when they are sick and young). But that is just me, everyone is different.
Wishing you strength.
"If love could have saved you, you would have lived forever." RIP my awesome Wolfie Dog