Re Burton Tandy...
NSW Govt Gazette page 1447 has a notice issued by the NSW Col Treasury, at Sydney 15 Dec 1847 re several pieces of land at Ipswich that were forfeited by Burton Tandy. They had been advertised previously in the Gaz of 6 Aug 1847, and sole by auction at Brisbane, Moreton Bay on 15 Sept, 1847.
According to that notice, two lots with deposits of £1 12s and £2 10s were each of 32 perches and another of 32 perches where the deposit/price paid (JM is not sure from the Gaz if it was deposit or full price) listed was £18 8s.
I think Burton Tandy would be noted in the Queensland Early Pioneers Index 1824-1859. Most likely the QFHS at this link will have further info
http://www.qfhs.org.au/ He also seems to be indexed in the Sth Australian as well as the NSW Govt Gazettes. in the 1840's.
Of course, it would well be that Bertha was married to a Mr Tandy when she was still a slip of a girl, perhaps as young as 12. But as mentioned several times there are flaws in the NSW BDM online index, presuming she became Mrs Tandy through marriage in the districts that formed NSW in those years 1845-1852. Have you checked SA marriages for any likely mention of any Mr Tandy marrying there?
Cheers, JM