Eric, it may very well be, as it seems to be that Ann Penrhyn stayed in England. It might account for me not being able to find her death notice in Australia. I am not sure where the following fits in but you might be able to place it:
South Australian Chronicle: ASTON. — On the 25th April, at Crafers, Susannah Rebecca, daughter of the late John Aston, Esq , of Aston, Warwickshire, England, and of Ann Penrhyn, his wife, of Penrhyn, Wales.
Rebecca Penrhyn Aston, married Edward Smith 27 Dec 1855 at the bride's residence, Queenstown, South Australia.
Priscilla Sarah Aston died May 1866 at Crafers, South Australia, beloved wife of Edward Smith.
South Australian Advertiser: 9 Dec 1876, Webster.—On the 4th December, at the residence of her son-in-law, C. W. Hamilton, Esq., Mount Pleasant, Susan Isabella, the second daughter of Christopher Penhryn Aston, Esq. of Bayswater, London, and the dearly beloved wife of William Frederick Webster, of Port Wakefield, South Australia. London TIMES please copy.
Sydney Morning Herald: 14 Oct 1924 “IN THE SUPREME COURT OF NEW SOUTH WALES.-Probate Jurisdiction.-In the Will of FREDERICA PENRHYN ASTON HAMILTON late of Walkerville-road St. Peters formerly of North Adelaide in the State of South Australia Widow deceased. Application will he made after fourteen days from the publication hereof that Probate of the last Will of the abovenamed deceased granted by the Supreme Court of South Australia Testamentary Causes”
South Australian Register: 14 May 1924 “HAMILTON.— On the 13th May, at Private Hospital, North. Adelaide, Frederica Penrhyn Aston, widow of the late Charles White Hamilton, formerly of Mount Pleasant. Peace, perfect peace.”
Let me know how these fit it and I'll look up some more material for you.