Honorary Promotion In Retirement

Compo claim from who? Generally the Army only pays out extra if they caused the accident.
Not sure - it was submitted through Lawyers. All we had to provide was a predicted summary of potential future rank he may have reached, based on his Report Profile and MCM Div Statistics.
In some cases it works in the claimants favour, in other cases it doesn’t!
In this particular case, it was quite straight forward to declare he would have been a strong candidate for LE Commission and a second career up to the minimum rank of Major.
The thinking behind the question is based on 3 years working at APC. Granted, it was over 16 years ago and I was a different cap badge, but the principle remains the same. To be considered for promotion to WO1, you must be selected at a Board held annually at the APC. If my memory serves me well, the WO2 to WO1 Board is (or was) chaired by the 1 star Head of Arm (now OF5), with a couple of COs, SO1 Soldiers, and the Corps RSM making up the 5 Board members, with SO2 Soldiers as the Secretary.
If she was selected on this type of Board and didn’t pick up her appointment because of a career ending injury, I suspect she was eligible for financial compensation rather than ‘Honoury’ retrospective promotion, which is not something I’m aware of.
I can say that I was involved in a Compensation claim for a R Signals WO2 (male) who was selected by a Board for promotion to WO1. He was involved in a serious motor cycle accident and medically discharged from the Army before he took up his (RSM) appointment. He was (is) a good egg and had excellent potential.
The Corps supported his Compensation claim (based on missed promotion and potential LE Commission) and he was awarded a substantial pay out.
Did your friend receive similar compensation?
Kind of similarly, I know a bloke who was an A/WO1 RSM, then got sacked by his CO and reverted to to WO2. He was posted to another unit and started to have bad psychological issues. In the meantime, he came off the board again for WO1, but was then discharged for medical reasons. He went through the tribunal system and it was deemed that his initial sacking was unfair and that led to everything else.

Through the tribunal, a deal was done with the MoD that he would receive a pension as if he had received an LE SSC and completed it.