I waited until Uni was almost 4 years old bc of the same reason as you! I was so nervous to do it, but never wanted her to have puppies. I finally found a vet I love and they did her surgery. I had bloodwork done a few days before hand. She was fine by the next day. It was the BEST decision I ever made for her. Also she was such a picky eater before, now she eats like a champ! So much less stress for me now.
I also cried like a baby when I dropped her off.
She will be fine. Just talk with your vet about all your concerns.