Another curious question.
So, if the airline decides to refuse selling a ticket to her given her mobility (or lack thereof) is a greater risk to the fellow passengers in emergency, do the airline gets punished/sanctioned for such refusal in EU?

Discussions above relating airline failing to satisfy the contract made me think then what if there was no such contract in the first place, i.e. airline did not sell a ticket, that is also considered discriminatory?? So, the airline will be blamed either way, refuse to sell - discrimination, sold ticket but unable to accommodate - discrimination?