My heart truly goes out to you and your little wow, I know EXACTLY what you are going through and the gut wrenching anxiety that goes with this situation, please try to sleep as much as you can and eat properly,, last thing she needs is someone so jaded and 'out of it' that things become out perspective and so depressing there is nothing but sorrow and darkness, and try generate positive feelings for this little sick dog.
If you get really down talk to someone who understands, who has been there, I did that once in the past at a VERY bad moment, and trust me, it helped more than I dreamt possible, I hope you have people around you to turn too......I have everything crossed for Milly....Be focused and concentrate on what you can do for her not what you cannot