Driving test and wearing a mask

Hi my daughter is due to take her driving test soon and is worried about having to wear a mask as it makes her glasses steam up and this makes her anxious and this together with the anxiety of the driving test is going to make things a lot worse.  She also has a  processing  disorder and when she is a anxious or nervous this makes it even harder to understand instructions.  Can we say she is exempt from wearing a mask during her test and if so is there official document we need.