While equipped, increases experience gain for Skills by 10%.
Sources
Kylie (Trinket) can only be obtained by using a Hyper-Dense Neural Chip on the tank containing Kylie Muir's disembodied brain in the Robotics sub-section of the Hydroplant.
Trivia
In 0.10.0, Kylie's effects were swapped with that of the Pet Rock (Trinket).
The description "You made her a promise, remember?" could be a reference to dialogue between John 117 to Cortana (an AI similar to Kylie) in the Halo Universe, where John promised to return to Cortana.
There is a special interaction that occurs when talking to the Waterbot found in Power Services. While having the trinket equipped or in their inventory, Waterbot will point out to the player that they forgot to enable Kylie's speech function, her voice. It then greets Kylie, and Kylie speaks in her own voice to greet K18.
Once this interaction happens, Kylie will occasionally speak to the player while being equipped. She shows concern and offers encouragement while players are in combat, warns the player of the appearance of IS-0091 and she will bid players goodnight whenever they sleep.
As of 0.10.0, this does not influence the gameplay or story of the game.
You get another special interaction with Kylie if you read Wakeman'sEmail in his room within Residence Sector with her equipped, revealing his intentions with Kylie. She will remark that she isn't a tool and that she trusts the player.
When interacting with the Sun Disk, Kylie will remark that the device speaks to her. It says something about the truth of our Sun, that we aren't ready to hear yet.