I must admit that I am a little surprised at the backlash to sisemen's post. And would like to throw my two cents worth into this interesting discussion.
Beforehand, I commend Tightslop for not closing this thread - you appear to be more liberated these days.
Anyway, we have to assume that the OP really did see this person and correctly described the size of this person - I.e not being able to get out of an over wing emergency exit. How can any of you disregard straight away or contradict what the OP saw in order to strike up this debate/discussion. Were you with the OP at Perth?
Secondly, we know Australia, just like we know the UK, or the US - basically any western leftist country where if you so much as look at someone the wrong way, you can be accused of ageism, racism, sizeism, etc ad nauseum. Therefore it is quite plausible that IF this woman of certain acreage is employed by QANTAS, one can deduce that QANTAS might be reluctant to get their noses in the press by being accused of discriminating against fat people.
Anyway, this is just my opinion playing devils advocate. The OP may well be over exaggerating in his sizing up of this woman but we have to take his word on this. Therefore the discussion has been made - if this woman can't fit through an emergency exit, should she be given ground duties instead? This is what the OP is asking.