Well, unless she's discussing how the boiling point of water changes with the weather or altitude (barometric pressure) - I would stick with 212ºF. That's what the thermometer makers suggest for calibrating them.
For example, at standard 1-Atmosphere sea-level barometric pressure (29.92 inches Hg) - water boils at 212ºF. But, you have a high-pressure system sitting over you and the barometric pressure is 30.5 in/Hg - the boiling point of water is 213.07ºF. If you've got a low-pressure system sitting over you and the pressure falls to 29 in/Hg - the boiling point falls to 210.3ºF.
If you can find out your barometric pressure - you can use this Pressure Corrected Boiling Temperature of Water Calculator
If you have an old-fashioned wet-blub analog candy/fry thermometer (the kind with a liquid that rises in a glass tube) you can use that to determine the boiling point of water - and adjust your instant-read accordingly.
RE: Calibrating Instant Read Thermometers
There are two types - analogs that use springs and have a pointer dial, and digital. For the analog type - they should be calibrated on the high end of the scale - since that is where you are going to be using them. For digital types - they usually have two calibration settings - the Zero and the Span ... you calibrate the Zero setting for ice-water (32ºF) and the Span for boiling water (212ºF).