I can understand not wanting to make a scene but that's exactly what she should have done. Previous UK disability activists when appearing in TV studios wheeled into the stairs and flop out of their chairs onto the floor to highlight the problem of poor accessibility.
It is, but I think we can cut her some slack on freezing up in a posh situation, in shock at having been blindsided by that insult. She did make a scene after the event, which is why we're reading this. I assume there were other awardees, whose reaction/support she couldn't count on if she interrupted their ceremony and turned all the attention to herself.
It is fair to cut her some slack given that she likely was blindsided by the lack of accessibility, not every battle is worth fighting. But any opportunity to embarrass the City Of London Corporation is fair game given the absurdity of pomp and ceremony they surround themselves with.