I do feel for you, and most of here will have been through this before. Only thing I can add is that with my first dog, although I was in the room (we had it done at home), I couldnt bring myself to hold her, and I have regretted it ever since. With my boy I held him in my arms, and talked to him, I was beside myself, and cried uncontrollably afterwards, but I had to be brave for him. I understand you wanting to spend some time with her, but you could be causing yourself more pain.
Chin up, she knows you love her, and this is the kindest thing you can do for her. She will leave a paw print on your heart forever. x