At the 2012 Olympic Games in London, Weightman ran a personal best of 4:02.99 in the 1500 metres semi-finals, and went on to finish ninth in the final. In 2013, she ran a 3000 metres best of 8:43.46 in Stretford. She further improved her 1500 metres best to 4:00.17 on 5 July 2014 at the Paris Diamond League. She won a silver medal at the 2014 Commonwealth Games in Glasgow and a bronze medal at the 2014 European Championships in Zurich.