The daughter of J.N.R. Millett, a curator of the Penzance Natural History and Antiquarian Society. With her sister Louise Millett, they contributed scientific papers and models of dolmen and standing stones for the Society.
In 1864, the sisters also contributed writing on the wildflowers of the Scilly Isles to the Transactions of PNHAS, returning from the islands with a list of 'one hundred and fourty-six flowering plants and sixteen ferns' they had observed.
In 1861, Matilda also authored a paper on the remains of the Iron Age hillfort, Chûn Castle, for the Transactions of PNHAS.
For mention of the Millett's models within a broader view of Cornish antiquarianism, see Naylor, S. 'Collecting quoits: field cultures in the history of Cornish antiquarianism,' Cultural Geographies 10, 2003. pp. 309-333