Elizabeth Church Pottinger was buried in EI on 29 Jan 1800 aged 79.
Ann Lambourn, there are a couple of candidates for her among my own connections so I don't think she was ever a Pottinger. (Having said that, one of them was a COKE before she married and I don't know where she came from, so there might be a connection there.)
The Pottinger-Coakes marriage entry unfortunately doesn't give any status, only that they were both of the parish. It was a marriage by licence though, so that might reveal something. There was a Coak/Coake/Coakes family around up to the 1750s, they had a Mary but she seems to have died young.
No death for Elizabeth Pottinger in EI or Compton, and nothing that fits in the BBI. I think it's most likely that she married after Letitia/Melytia was born. Not in EI or Compton though.