In reply to JuneBob:
That sounds to me like the lower shin buckle and the buckle in front of the ankle may be done up too tight, perhaps in an attempt to reduce heel lift caused by the narrow ankle?
TBH I think your friend may be on a hiding to nothing expecting a rental shop to do anything more than a cursory boot fitting. They tend to be oriented towards shifting in and out large amounts of kit that is more or less right for more or less averagely shaped people. People with troublesome foot shapes that need specialist boot fitting, even straightforward stuff like moulded inners and shell reshaping, aren't going to get that at a rental shop.
I would suggest that your friend may have to bite the bullet and seek advice on a pair of ski boots for herself from a specialist ski boot fitter, such as Profeet in Fulham. A pal of mine is very pleased with the boots he got from them a few years ago, having finally had to ditch the Salomon rear-entry boots that he'd been skiing in since the mid-1980s(!), and then struggled to find a modern boot that wasn't agony. These sort of specialist fitters are a step up again from the boot fitting services generally offered by the "high street" retailers such as Snow and Rock, and Ellis Brigham, which IME don't go any further than selling you Superfeet insoles and moulded inners (which are all very well as far as they go - I use Superfeet insoles very happily myself - but won't necessarily be sufficient for the most problematic foot shapes).
Another pal of mine wasted huge amounts of time and money, and spent many seasons of discomfort on the slopes, trying to find a well-fitting ski boot from various mainstream retailers. It was only after he went to a specialist ski boot fitter that he was able properly to enjoy his winter pastime without pain.
Life - and the average ski holiday - is too short to ski in painful boots.