Remnant Population

Ofelia is tired: tired of being told her how to act and what to do, tired of living with her son that doesn't listen and her snippy daughter-in-law, tried of people. They all live and work as employees in the Sims Bancorp colony #3245.12, until the tide of business fortunes turns out of Sims' favor. They've lost the charter for the colony and are making everyone ship out to space in cyro-sleep to start over again.

For Ofelia this is a golden opportunity. When the time comes, she gives everyone the slip, staying behind on the colony, intending to live out the rest of her life in peaceful solitude with her house and her garden and the comforts offered by all the colonists had to leave behind.

The piece is broken by the arrival of another colony ship - thousands of miles away, but heard by Ofelia on the old communication equipment - as they try to land and are massacred by a gang of angry aliens that no one knew existed on the planet before.

The natives - The People - are reminded of another event, years ago, where machines were seen making scars across the sky in a place far away from their home nests; could there be more of these invading monsters here? A party of them set off to investigate...

As a result, Ofelia gets caught up in a culture not her own, as she slowly learns that the creatures have not come to kill her but to watch her, and though they first seem much like ignorant children, they have a lot of surprises in store. And in the end, it will be small, insignificant, harmless Ofelia who stands between them and the humans.

Remnant Population is a standalone novel by Elizabeth Moon, a decidedly non-Space Opera offering from a writer best known for them. Ofelia and her internal conflicts make up the core of the story, with a side of lampooning the concept behind Star Trek style limits on interacting with alien cultures.

Tropes

 * Alien Non-Interference Clause: The human governments have one of these in spite of never having met aliens before. The human preconceptions get severely deconstructed when they meet The People.
 * The Chosen Zero: Ofelia is old, weak, frail, a woman of Stay in the Kitchen upbringing and used to being dismissed as unimportant. And she has to stand up to humans with official titles and college educations and guns? She doesn't consider herself worthy of the People's trust (or potential sacrifice if it came to violence) but the People do. Firmly.
 * Closer to Earth: Ofelia is fairly simple and apparently unimportant, likes peace and quiet and prefers working in the garden and making clothes and jewerly as passtimes but she has the wisdom of age behind her.
 * Dumb Is Good: Averted and played straight at the same time. Averted because Ofelia is resentful of her culture punishing her for being too smart as a child; as a result she's very intelligent but has low-to average education, and ended up raising her children with the same prejudices. Also because the People consider the quest for knowledge one of their highest virtues, and the facility of that one of the qualities of a good nest guardian. Played straight because Ofelia, who is Book Dumb compared to the human scientists who come to study The People, is wise enough to see them for what they are, while the college-educated Ph Ds are lost in their own taught prejudices.
 * First Contact - Humans have been colonizing space for years but this is their first encounter with another species.
 * I Choose to Stay - Ofelia
 * Mama Bear / Papa Wolf - You do NOT mess with The People's nests/children. In their culture's it's unthinkable.
 * One Nation Under Copyright - Sims Bancorp signs on colonists as employees for life or until they're considered too old to work anymore - Barto and Rosara would have had to pay extra for Ofelia to travel because her contract was up - appear to run a "company store" sort of system and have the ability to overrule the desires of the colony. We never see most of the Mega Corp trappings in person but it's implied that there's good reason their fortunes turned against them.
 * Starfish Aliens - The People are hard to describe succinctly - skin like soft leather, legs like an ostrich but backwards, taloned hands with four fingers and opposable thumbs, eyes like reptiles or a cat - but no one will mistake them for looking like humans.
 * Xenofiction: Ofelia is the main viewpoint character but there are a few interludes that take place from the People's point of view.