I'm not an expert and certainly hope it's not the case, but wonder that if going against medical advice to undergo a hysterectomy at the time, could cause her insurance company to deny covering the surgery at a later date? Much cheaper to do it all at one time than 2 separate surgeries.
Not that health decisions should be based on this, but in the US medical cost is often a deciding factor that wouldn't occur to us with the NHS. For the insurance companies, it's all about the bottom line.
Also, I'm surprised she didn't technically give written consent for a hysterectomy. Is it not normally something you're warned about as a possibility if medically required during the consent discussion before signing the paperwork?
It was a while ago, but I'm pretty sure I had to give consent for possible hysterectomy during my tubal ligation with c-section in the US. I tend to trust the medics judgement on medical matters and consented knowing that my family was complete and I had chosen to be sterilised in any case. (The hysterectomy came later back in the UK.)
I was surprised they removed her cervix too. Could there have been HPV cervical pre-cancer presence too? They left an ovary, so I don't think it was a case of just whipping everything out willy-nilly.