I'm very sorry about your loss. Please know that you were trying to do the best for her throughout her entire life, including making the decision to spay your bun. You were well educated about the problems of NOT spaying (namely unwanted pregnancy and the high incidence of uterine/ovarian cancer in female buns) and did what you thought would make your little one's life healthy and happy.

Sometimes, unfortunately, surgery can cause complications for buns, but you were trying to keep her longterm health in mind. I myself was very nervous about neutering my 6 month old male bun. You are a wonderful bun caretaker, and will no doubt continue to bring happiness into the lives of your other buns:-)