My memory of this story is very thin indeed. It was in a SF digest or anthology in the mid- to late 90s. Read in New York City, but could have been written anywhere (but from what I remember of the writing style, likely American).
A human xenolinguist or xenoanthropologist gets her big break and is assigned to make first contact with a civilization on a planet. Her ultimate aim is to bring them into the fold of some kind of larger galactic federation of many planets and species (the body which has assigned her to this planet). Assimilating planets and new species is a common but prestigious process in this society.
Her assigned planet is populated by what are effectively anthropomorphic rabbits. Like, completely unapologetically, giant rabbits. Her first task is to establish communications with them.
They’re friendly and welcoming (portrayed as gentle though somewhat dim), but she discovers an enormous obstacle to communicating with them. They simply cannot conceive of (and therefore use or understand) counterfactual language.
For example, “if I had been there, I would have stopped the fight” is completely incomprehensible. They can’t get their heads around it. This is the device that drives the entire plot.
Eventually she discovers a single individual whose thinking is just different enough to be able to get the lightest handle on counterfactual statements. Using this ability, this rabbit becomes the savior of her program in some way. I have a vague, potentially unreliable memory of some kind of mirror or portal which served as the commutations back to the higher-ups, being both a prominent element as well as the place she had to bring this idiot-savant rabbit to demonstrate she’d succeeded in her assignment.
The overall tone of the story is humorous, lighthearted, and absurd.