- Her biggest success came in 2013 when she led the New Zealand under-21 side to a surprise victory at the World Youth Cup in Glasgow, where the New Zealand team toppled the highly touted Australian line-up.
- Southby also led the Fast5 Ferns from 2013-2014, winning the world title in both years.
- A former Otago Rebels player, Southby served as assistant coach to Dame Lois Muir at the franchise in 2005, before taking on the head coach role from in 2006-2007.
- Along with Dame Lois, she has received mentoring from Lyn Gunson, Leigh Gibbs and outgoing Silver Ferns coach Waimarama Taumaunu.
- Silver Ferns shooter Jodi Brown, who announced her retirement following New Zealand's 11-goal win over Australia in Friday night's final Constellation Cup test, is Southby's sister-in-law. Brown is married to Southby's brother, Markham.