Under the AF06 certain offences must be reported to the RMP by the OC. These include most assaults and all those in a training establishment.They might get involved if there is a murder or rape, but otherwise it no civilians are involved it will be the old favourite police saying 'not in our remit mate, down to the RMP.' Even a major investigation would be in conjunction with the SIB. If are are allegations of assault she could make a report to her local police who under National Crime Reporting Standards should report it and pass the allegations to the RMP as the investigating authorities.
The complaint must come from the person involved.
It‘s not easy being a victim of crime, so @Army mama , be aware it could be complex, lengthy, and you may not get the result you want. That is not to put you off if justice is sought (and gained).
I wish you both all the best.