The 21-year-old from Birmingham was wearing a black crop top with orange trousers when she boarded the plane to and said she passed through check-in and security before anyone mentioned anything about her outfit.
But at the gate in Birmingham airport, the trouble began.
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'.
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".