The Tasmanian Civil Registration records 1803-1933 have just been made available to browse on FamilySearch:
https://familysearch.org/search/collection/2125029
I'm not sure how to find a particular entry once you have got the right place, event and year, though, other than browsing through page by page, if you don't already know the registration number. (I think you would have to look at the Hobart records for Helen's death.)