The strange thing in the closet

The first time Steve met Riley, he was nine years old. The strange girl that had appeared in his closet. A girl out of her own time but also a link to that time. Will she decide to stay in her time or will she forgo the future for her place in the past? Will her secret be kept or will the town of Hawkins find out she's not in the right time? How does this affect out favorite group from hawkins?