Howarth was born in Hamilton, and resides in nearby Cambridge. She has a congenital bilateral arm deficiency, with no right hand and her left arm ending below the elbow.[4] She attended Cambridge High School.[5]
Howarth started swimming at age "three or four" and started swimming competitively at age seven. At age eight, she was inspired to compete at the Paralympics and win a gold medal after 2004 Olympic cycling gold medallist Sarah Ulmer visited Howarth's school.[6] She is classified S7 for freestyle, backstroke and butterfly, SB8 for breaststroke, and SM7 for individual medley.[7]
At the 2015 IPC Swimming World Championships in Glasgow, Howarth won two gold medals in the 50 m butterfly S7 and the 200 m individual medley SM7,[9] qualifying her for the 2016 Summer Paralympics in Rio de Janeiro. She was officially confirmed to represent New Zealand at the Paralympics on 5 May 2016.[1]
While competing at the International German Championships in Berlin on 9 June 2016, Howarth set a new world record in the women's 100 m butterfly S7 with a time of 1:18.65, taking 1.49 seconds off the previous record set by American Mallory Weggemann in 2009.[10]