Brian I replied under original heading - however further thoughts.
There was no need to register any death pre 1877 (the English Act virtually required this from 1837 but it was possible to avoid registration, the loophole was tidied up in 1872 and the Manx 1877 passed on the later English Act). The churches (as monopoly suppliers of burial grounds required burials in such grounds be recorded - the burial registers we all use) if you could find a burial spot elsewhere then such registration may not have been necessary but custom generally required a burial in hallowed ground.
There was no requirement to produce a will - numerous parties died intestate - the church (via its spiritual courts) was involved here but things were moving to be much along the lines of the English probate system at this period of 19th - if there was no property then no administration would be required.

The only surprising ommision is a burial record for Christian - check that she is not under a maiden name or a transcription error - if as seems likley she, a poor widow,was buried by the parish they may not have been too careful to correctly record all details