St Peter Port Possible Baptism

[Nara]

This is a massive long shot but here goes:

SOPHIA LOUISA EGERTON
My 5xGG is very elusive. People have been researching years and we have yet to find any baptism for her.
Some tree's on Ancestry have her baptism as possibly St Peter Port? Guernsey but I cannot find any records to prove this.
She died in 1838 before any census and her age at death would have meant she was born around 1776, No one has any evidence to prove who Sophia's parent's really were.

She married a Thomas Havelock and at least one of their children were baptised in St Peter's Port - Anne Havelock b 1801 but there is also no baptism I can see for her, but on the censuses it recorded Guernsey as her place of birth. 

Any help much appreciated 

[ColC]

I note one tree on Ancestry has the birth noted as below but this type of information is not always reliable.

1775 Guernsey, Poweshiek, Iowa, USA

Colin