Hi earlybird,
You may have already found out the information you are after, if not the following may help.
Elizabeth Peters (Harris) death cert. says that her father was John (a miner) and her mother was somebody White. It also says that she was born in Camborne in Cornwall. I have found a John Harris who married an Ann White and had son John Baptized in Camborne on 2nd Jan 1820. The only possabilty found of Elizabeths baptism is in Tywardreath Cornwall on the 24 Aug 1828. She is shown as the daughter of John (a miner) and Ann Harris.
Her birthdate may be from 1824 (death cert.) to 1826 (Marriage cert.).
There is a record of a John Harris b; 1819 arriving in South Australia on the Houghly (the same boat as Elizabeth) -occ Miner, Montecute married to Alice Smitham in Linskeard, Cornwall in the Jun 1/4 1845.
Montecute is where Elizabeth & her husband,Thomas Peters' first two sons were born.
The marriage cert. of John Harris and Alice Smithem says they were married in the Wesleyan Chapel in Liskeard, Cornwall on 17 May 1845. They were both resident at St Cleer at the time. Both their fathers (John Harris & Nicholas Smithem) were Miners. I think John Harris snr. may have died before 1841.
I hope this has been helpful.
Regards Ding.