Feel free to read the provided lines here, or from episode five's script.

Esmeralda is a ghost girl who died in the 1950s.

Esmeralda is one of the many ghosts living in the Hamilton House. She is the first ghost Clair meets in the house.
Esmeralda follows Clair home and requests that she help the main ghost of the house move on, because the mysterious ghost seems to be very angry and restless.

Although Esmeralda doesn’t remember how she died, or much about her past, she is a happy spirit. She still feels lonely like all the other ghosts in the Hamilton House, but she doesn’t let that keep her down.