She claims she was repeatedly asked by cabin crew to cover up - first as she was boarding the plane, and subsequently by a group of the plane's staff who surrounded her in her seat and claimed her outfit was "inappropriate".
Accompanied by a photograph of her at the airport before the flight, O'Connor wrote on Twitter: "Flying from Bham to Tenerife, Thomas Cook told me that they were going to remove me from the flight if I didn't 'cover up' as I was 'causing offence' and was 'inappropriate'.
"They had four flight staff around me to get my luggage to take me off the plane."
The trainee accountant added that when she refused to change what she was wearing, a manager went to get her bag in order to remove her from the flight.
She said: "A man then shouted 'Shut up you pathetic woman.'
"I was given a jacket by my cousin sitting at the front of the plane and they did not leave until I physically put it on.
"They made comments over the speaker about the situation and left me shaking and upset on my own."
Thomas Cook has now apologised to O'Connor and a spokesman said the airline was "sorry" to have upset her.
He said: "It's clear we could have handled the situation better.
"In common with most airlines, we have an appropriate clothing policy.
"This applies equally to men and women of all ages without discrimination.
"Our crews have the difficult task of implementing that policy and don't always get it right."
The policy referred to by the airline outlines that customers wearing "inappropriate attire (including items with offensive slogans or images) will not be permitted to travel unless a change of clothes is possible".
