Betsy worked as a clerk in her father's shipping office until 1827 when her brother Hugh died at the age of 34 in a drowning accident at Ardrossan Harbour. Shortly after this incident her father agreed to let her take her brother's place on board his ship 'The Clytus'. When Captain William Mille retired due to ill-health in 1847, Betsy became the first female Captain of a British ship to be registered in the British Register of Tonnage.
Captain Betsy Miller was master of the two-masted brig, sailing with coal from Saltcoats to Dublin and bringing limestone back to the Ayrshire Coast. She captained the ship and the 14-man crew until 1862 when she retired aged 70. On one occasion the Clytus ran into danger off the Irvine coast, with Betsy claiming to cry...
"Lads, I'll gang below and put on a
clean sark, for I wid like to be flung
up on the sawns kin of decent. Irvine
folks are nasty, noticin' buddies".
The crew later attributed the safe return of their ship to the change of clothing!
Betsy died on 12th May 1864, having succeeded in paying off family debts of £700 and living with her sisters in relative comfort. The Ardrossan and Saltcoats Herald of 1864 described her as having: "redeemed honour, secured a competence, performed a noble sisterly duty and, in her humble sphere, gained a name honourably mentioned both in her own country, and in the States of America". Betsy's youngest sister Hannah took over the management of the Clytus and was continuing to ply trade with Irish ports.
In 1890 Hannah died, the last survivor of the Miller family. The Clytus was sold, but continued to trade from Troon and Ardrossan throughout the 1890's.