She saw the MNer being ill, assumed she was receiving benefits and started to abuse her.
Now I think about it, I remember reading about a similar incident on MN. Not sure if it's the same one, but it was in a cafe and resulted in water being spilt on someone's shoes. Then they got abusive.
I wonder if they didn't realise the person was ill. A full on fit would be obvious and I honestly can't believe that anyone would go into abusive mode while someone is thrashing around.
A mild attack, e.g. a short loss of awareness, could look like clumsiness or possibly out of it due to alcohol/substance abuse. But if that's the case it wouldn't have been disability bashing, iyswim.