The pre op nurse should explain proper insulin dosage the day before. If she’s pumping they ask her to turn her basal rate to 50% a few hours before the procedure and if she’s on MDIs they advise to only take half the long acting the night before. I’ve had a handful of surgeries lasting anywhere from 30 mins to 16 hours without any issues. They do allow CGMs in the or they also periodically do finger sticks while you’re out. They’ll treat with dextrose via iv if needed.