No she couldn't have, she had a broken leg, holy stuff the worse that could've happen is her leg being unusable.
A lot.
The simplest mistakes can kill in surgery.
Even in a very basic surgery, anything can happen, from infection (Which is rare, but not impossible), bleeding (Sometimes surgeons make a mistake and can cut parts of the body) to material being lost in the body, whether that's surgical equipment, bits of bone or other material that was already in the body damaging it.
This is why the option to take surgery is always, if possible, the last option to be taken.
Being put under the knife can still be risky, even in this day and age.
Congratulations on coming out healthily though.
Here's hoping you feel better all around soon.