Budd practiced Muay Thai for many years and later became the only woman to defeat American Gina Carano in Muay Thai competition. Her second and final loss in the ring came by Germaine de Randamie, after which Budd made the move to MMA. Her Muay Thai record is 10–2. She began training in MMA at the end of 2008 and avenged her loss to de Randamie when she defeated her via unanimous decision in a 2011 MMA bout. Budd trains at the Gibson Kickboxing & Pankration Academy.
Budd made her MMA debut on at Strikeforce Challengers 11, defeating Shana Nelson via TKO in the second round. In her second fight for the promotion, Budd was knocked out in 14 seconds by Amanda Nunes at Strikeforce Challengers 13 on. On, Budd faced Germaine de Randamie in a rematch under MMA rules at Strikeforce Challengers 16. She defeated de Randamie via unanimous decision. Budd's final fight for Strikeforce came on when she was submitted by Ronda Rousey at Strikeforce Challengers 20.
Invicta Fighting Championships
In 2012, Budd signed with Invicta Fighting Championships and faced Swedish fighter Elina Nilsson at ' on. She defeated Nilsson via TKO in the first round. Budd returned to Invicta FC on at '. She was originally scheduled to face Elaina Maxwell, but Maxwell sustained a concussion in training and Budd instead faced Danielle West. She defeated West via TKO in the first round. Budd was scheduled to face Ediane Gomes at ' on. However, on, it was announced that Invicta FC had signed Cristiane Santos to face Gomes on the card and Budd was to face Australian Fiona Muxlow. On, Invicta FC announced that Gomes was injured and that Muxlow would now face Santos. Budd remained on the card and instead faced Mollie Estes. She won the fight via submission in the third round. Budd was again scheduled to face Ediane Gomes at ' on. However, she suffered a neck injury and withdrew from the fight on. On, Budd faced Charmaine Tweet at. She won the fight via unanimous decision.
Bellator MMA
In August 2014, Budd signed with Bellator. Budd was expected to make her promotional debut at Bellator 133 on February 13, 2015 versus Talita Nogueira. However, Nogueira pulled out of the fight due to a knee injury, so Budd instead faced Gabrielle Holloway. She won the fight via unanimous decision. Budd was set to face former Strikeforce Women's Bantamweight ChampionMarloes Coenen for the inaugural Bellator Woman's Featherweight Championship at Bellator 155, however Budd got injured and was replaced by Alexis Dufresne in a non-title fight bout. Budd faced Arlene Blencowe at Bellator 162 on October 21, 2016. She won the fight by majority decision. Budd faced Marloes Coenen for Bellator's inaugural women's featherweight championship at Bellator 174 on March 3, 2017. She stopped the veteran Coenen in the fourth round via strikes after securing the full mount position. In her first title defense, Budd faced Arlene Blencowe in a rematch on December 1, 2017 at Bellator 189. She won the fight by split decision. In her second title defense, Budd faced Talita Nogueira on July 13, 2018 at Bellator 202. She won the fight and successfully defended her title via TKO in the third round. In April 2019, news surfaced that Budd had signed a new, four-fight contract with Bellator. In her fourth title defense, Budd faced Cris Cyborg on January 25, 2020 at Bellator 238 in Inglewood, California. She lost the fight via technical knockout in round four.
