That's for you to decide Phil, but I'd advise you to sleep on it a bit. Remember you don't get paid for work place representation, and believe me, it can heavily eat into your time, cause a lot of stress, and doesn't stop when you clock off. Ultimately though, if you feel sufficiently moved to stand up for right in the face of wrong, it can be rewarding, but you frequently find yourself being shot at by all sides. Its clearly not without its responsibilities too, and you can end with peoples livelihoods and even sanity hanging on your ability to get them out of a situation. To a large extent if you're doing it properly, it will almost certainly bring you into conflict on a semi regular basis as well, and not just with management incidentally either
However, if you want to be the discreet knight in shining armour, you might consider having an off the record chat with your colleague and advise her that it might be prudent to start keeping a log of dates and times of any incident involving the Manager that she encounters in the next 18 months, that might be capable of being presented as discrimination, victimisation or bullying etc. It's been my sad experience that thwarted once, the manager (a bit like a circling shark) will come back and have another ago in the future. A personal diary (with a note of witnesses to any incidents - and ideally testimony) is normally admissable evidence in any future hearings, and should carry some weight.
I should have said starting with todays incident. Most medical disciplinaries are supposed to be conducted in the spirit of idetifying a problem and putting in place a supportive mechanism to bring about a correction. Failure to observe this starts preparing the ground for a wrongful dismissal claim, but hopefully it never gets that far, as you normally hammer in a grievance, and win it for them being out of procedure. It's important to know what policy or procedure is being invoked. A similar thing will happen if they choose to go down the medical referral route. It's worth remembering that any policy or procedure is only as strong or as weak as the manager administering it Phil, but I'd log todays incident, and register concerns about how the process wasn't followed.