at one level there is no such thing as a right of way - the highway code only uses that term to say that it doesn't exist... what you have is priority...
however there is a hierarchy of vulnerability now which means basically that lorries give way to cars / cars to motorbikes to bikes to people etc.
there is also a requirement in the highway code to do everything you can to avoid an accident
regarding the yellow box - either you were already crossing when she entered it - in which case she should not have entered as her exit was not clear
or you weren't in which case you would not have been half way across and she would have been fine...
so
- her use of the yellow box was wrong (exit not clear)
- her not giving way to a more vulnerable user is wrong
- her not giving way to a pedestrian already crossing a side road
basically she is completely out of order and could have had the book thrown at her...
Rule 174
Box junctions. These have criss-cross yellow lines painted on the road (see ‘Road markings’). You MUST NOT enter the box until your exit road or lane is clear. However, you may enter the box and wait when you want to turn right, and are only stopped from doing so by oncoming traffic, or by other vehicles waiting to turn right. At signalled roundabouts you MUST NOT enter the box unless you can cross over it completely without stopping.
Rule 204
The road users most at risk from road traffic are pedestrians, in particular children, older adults and disabled people, cyclists, horse riders and motorcyclists. It is particularly important to be aware of children, older adults and disabled people, and learner and inexperienced drivers and riders. In any interaction between road users, those who can cause the greatest harm have the greatest responsibility to reduce the danger or threat they pose to others.
Rule 206
Drive carefully and slowly when
....
approaching pedestrians who have started to cross the road ahead of you. They have priority when crossing at a junction or side road so you should give way (see Rule H2).
Rule H2 - Rule for drivers, motorcyclists, horse drawn vehicles, horse riders and cyclists
At a junction you should give way to pedestrians crossing or waiting to cross a road into which or from which you are turning.