>>>Someone has yet to answer the question. Will you be penalised in the test for doing it?
Actually, if you read through your original post you'll see that you never asked it!
Your granddaughter needs to look at the test reports she will have been given:
http://www.a-class-driving.com/practical-driving-test.php
In particular she should look at Section 12, under 'Parking Brake'. If there's a number in the second box, that's the number of handbrake-related faults that were identified. It won't, on its own, result in a failure but it contributes towards the total number of points that have to be considered. However if there's a mark in either of the 3rd or 4th boxes ('serious' or 'dangerous') then it means an automatic failure.