Catherine Cookson's The Glass Virgin

At the age of ten, Annabella goes beyond the forbidden black door and sees her father cavorting with his mistress. Annabella faints and wakes only to be told that she just had a bad dream.

Annabella is eventually found by Manuel, the boy who taught her to ride horses. Manuel agrees to take Annabella with him on his travels.

Annabella and Manuel leave the Fairbairn's as he realizes he loves her. Shortly after, Manuel finds work in a glass factory, and they marry three weeks later.