This is the story of Johanna Howell as best I can make out. This is supported by publicly available documents but there is some speculation on my part. If anyone has private, family records that can refine the story better, please contact me.
There is no confirmed record of where Johanna was born. Her maiden name (Van Tassell) is documented once in death registration details of one of her children. While a connection to the Low Countries of Europe is implied by her maiden name, there is no other hard evidence. All three of her husbands served in the 57th Foot Regiment of the British Army. The postings for this regiment offer some tantalising suggestions. The 57th received battle honours in the Peninsular Campaign (1808-1813). They then joined the garrison in Canada before being recalled to Europe. They arrived too late for Waterloo. The 57th was then part of Army of Occupation in France, stationed in Belgium and France (1815-). I think it unlikely she met her first husband, John Collier, during ther Peninsular campaign on the basis of age and not being able to get there. The more likely event is the post Waterloo deployment. (Footnote: the 57th wasn't deployed with the Walchern expedition of 1808 so I don't think that was a candidate either.)
Being a camp follower was a hard life. In these years, they had little official status in the army. They marched behind the army on campaign and when a regiment redeployed by ship, the official number of followers allowed was small. A number would be selected by lottery to travel with the regiment. The rest would be abandoned. Apart from other comforts, they would have cooked, cleaned and tended the wounds for soldiers. Some would have been in service to officiers. Officiers were able to bring their families with them so there was a potential for camp followers to be in service to the officier's famlies.
There is another anecdote (source please!) that says that Johanna came to Australia as a servant to one of the officiers. Given the number of years she had been with the regiment maybe she had their trust. While there is no documentary evidence for this cited yet, we do see evidence of a connection with the Shadforth family. According to the regimental muster books, Lt. Col. Thomas Shadforth had number of servants with him when he same to Australia with the 57th. Unfortunately, their names are not recorded.
Johanna remarries after John Collier dies enroute to Australia. Her exact arrival in Australia is uncertain, but marriage record shows she was a widow who marries George Goldsmith of the 57th. Lieutenant Henry Shadforth of the 57th and son of Thomas is a witness to the marriage. Subsequently George retires from the army and takes up a selection at Cedar Creek, Wollombi. George dies before the five year term of the land grant expires. Although he had a written a will, the Colonial Secretary doesn't find the terms of the will binding. Despite this, the court was sympathetic to his widow's plight. The land is granted in trust to the Lt. Col. for the benefit of George's heirs, Subsequent to this, title on the land is recorded as passing from Shadforth to Johanna's third husband, John Howell.