i have been to a QF interview where they made you remove your shoes and if you had a 'large' hairdo they either made you take your hair out or they pushed the measure right down to your scalp. those that were outside of the height restrictions got asked to leave.
But like everyone else said, it may depend on who does the meauring and if they think that 1cm is a huge difference. Your friend may also be actually undermeasuring herself by 1cm and not know it.. regardless, i would tell her to give it a go, she has nothing to lose by trying and if she really is 1cm less then i would lie on the application and make myself 1cm taller! After all, its 1cm, not 5cm!