Your character collects something that no one else knows about—she doesn’t keep it secret, it’s just never come up.
(This will be another installment in the life of my alien character, Jade.)
Jade walked along the sidewalk with her two closest friends, knowing she was an outsider, but feeling the closeness of acceptance only true friends can bring. Janice and Ansiel had always accepted Jade, never questioning the odd green tone of her skin or her black almond shaped eyes. From the first day they met, almost six years ago on the boardwalk at Coney Island, the three had been almost inseparable.
New York made it easy to blend in with normal society. People may do a double take or openly stare a few seconds too long, but they would never say anything or draw attention to the fact Jade was different.
For six years Jade had lived on Earth, taking notes and marking observations in a worn black journal. Her assignment was for ten years - ten years before she reported back to the Superiors with all she had learned of this small planet.
Jade has collected many memories, marking them in her journal with a fine handwrite and occasional sketch. Janice and Ansiel knew of Jade's obsession with recording her day and this was also something they accepted without question.
But Jade kept her observations secret, never telling her friends that the things she wrote might lead to the downfall of all those on Earth. Jade never out and out lied to Janice and Ansiel, she just never went into detail about what she was doing.
Four more years - Jade only had four more y ears until her time on Earth was complete. After that time, she had no idea what would happen to the people - her friends - on Earth.