The Minimum / Living wage increases every April, there is also a "Real Living Wage", not legally compliant and is above minimum, which increases every year, it went up a whole 10% this year. What do you like to see in this respect?
How would you redefine a zero hour contract? A flexible and handy little earner, particularly for people who can't commit to regular working, people who want a little extra on the side of their day job, retired people topping up their holiday funds... or fleecing someone vulnerable who can't find alternative work? Not a loaded question, but you raise a good point of "redefining".
Public sector pay is complex and IMO shouldn't be considered any different to the private sector, maybe forgiving the armed forces as an exception.
I know this is pointy, but your mate should've considered her new wage before accepting, as anyone in the private sector would.