Sella works in the Environment department of the States of Guernsey. That position gives her access to planning applications and details of who owns particular parcels of land on the island.
She is a good friend of Simon Langlois and they sometimes go out for a drink together, usually on the balcony overlooking the Town Church. They don’t do this as often as they’d like, though, and Stella uses the fact that she hears Simon on the radio almost every day as the reason for forgetting how long it is since they last met.
Bonus fact: Stella first appears in The Sarnian book 2, but she wasn’t originally called Stella — she was Sheila. She isn’t the only character whose name changed during the writing process. Ross Ferbrache underwent a name change, too.