Sending prayers for her, and you.
My Maddie was about the same size and she did really well. When you drop her off it doesn't hurt to ask if she will be the first one done during the morning, some vets schedule multiple spay/neuter procedures for the day and if you ask that she is first then she wont have to go so long without eating. I also would recommend having her on IV fluids during the procedure. I am sure that Daisy will do really well.