dark matter, she was 7 went into space for 2 yeas but reversed how travel normally works and only was gone for 2 days.
Lol, that's an interesting take on it
And actually, with a bit of reworking, it could work. If the little girl was staying on earth and you travelled in a space ship at relativistic speed, then time would pass more slowly for you relative to the earth. So when you returned after a year, more time would have passed on the earth. Provided the young girl knew the speed you'd been travelling at (and had a crazy knowledge of relativity for a 7 year old) she could have calculated the relative times you would both experience.
However, there's a more mundane example that doesn't require accelerating you to significant fractions of the speed of light