Freestyle Libre 2

The Libre is reading interstitial fluid, rather than blood, so is about 15 minutes behind a finger prick test. Some people find that some sensors are more accurate than others, but often you will find a sensor is consistently reading the same amount lower or higher.
The sensor does take time to settle, so it can help if the day before the current sensor runs out, you apply the new one and don't activate it until the old one has finished. That can give better results from the time you start to use it.
Also if your granddaughter's finger prick tests are below 4 or above 10 the sensor can become very inaccurate.
If you have a hypo, the sensor can take longer to show blood sugar rising again, so always check with a finger prick.
Having said all that I love the ability to scan as many times a day as I want, and the ability to see trends, where your blood sugar is always rising or falling each day, enables you to achieve better control, and treat blood sugar that is rising or falling much quicker.
Hope you find it helpful.

You're welcome.
The other thing I've remembered, is that if your granddaughter lies on the sensor at night, this can give 'compression lows' where it falsely appears that you are hypo for long periods of time, so before treating for a hypo, it's worth doing a blood test.