Wow! Thank you so much for taking a look at this Pat. Great idea to use the name Matilda to make a connection, as it shows up no where on the Petch side. (Louisa is a family name on the Petch side, so looks like both sides were honoured with that one.)
One thing though, I don't think that Sarah and Matilda can be the same age. Sarah's daughter was born in 1880, so I think unlikely that Sarah was born ~ 1867. Also, both the 1881 Census and her death record put her birth date at 1863. Luckily, when you take a look at the original record, it looks like it might actually be a "9" (rather than the transcribed "4") which fits with the earlier birth date.
I really appreciate your tip about the Anglican records, looks like a field trip is in order. :)
Thank you so much for your insights - I think you've got me back on track!