From what I can make out:
The disabled scooter user boarded with her (small) scooter and then transferred to a seat where she would remain for the rest of the journey. At no point was the disabled woman sitting in the wheelchair space, nor was she ever evicted from it.
GWR policy is that scooters should be folded and put in the rack, unless there is a permit held. It is not clear whether the woman held a permit but it does seem very likely her small scooter was a foldable version.
The scooter user did not prebook assistance or a seat.
The scooter user was wrong in failing to fold the scooter, and placed her luggage on top of the scooter (someone else also did this was doesn’t help). It’s not clear why she failed to do this but the train was likely very busy and may well have been full of luggage. The scooter was placed in the wheelchair space. I am not knowledgeable enough to say whether that is reasonable.
An hour into the journey, a second woman (possibly with an arm injury, but I also note the disabled person’s companion was reported to have a broken wrist, so there may be some confusion) boards the train with a pram, baby and car seat. She is not disabled. The woman or her partner are occupying her reserved seat. The guard gets involved.
It seems the guard wanted the scooter out of the disabled space so the woman’s pram could go there. This is wrong. They should be folded and stowed in the racks, just like the mobility scooter. If the guard was trying to give a pram priority over a mobility aid then this is absolutely wrong.
The disabled woman has to leave her scooter in the vestibule as a result, and return to it at each stop to move it so passengers can board and alight.
At some point things escalate, everyone ends up coming across like an arsehole, not least the guard who then allegedly made an unprofessional announcement identifying the passenger as the problem, when it seems clear she only bears a limited amount of responsibility for what happened.