Her mother needed her in the house to help out. Any time she detected that her daughter was threatening to develop a life of her own, she would thump her cane. Having the reminder that mother was listening was the perfect romance killer.
So after the two went into the drink, there was the final scene. They were evidently inside a building, maybe a fish and chips place? Maybe in Holmfirth, maybe some place else? I have never really been able to figure the final scene out.
Beatrix Potter was in the same situation. We can perhaps thank Beatrix Potter's parents for the Peter Rabbit books. Beatrix was expected to spend her life, first and foremost, helping her parents. So she had to develop an income of her own in order to escape from her parents, hence the books, and she was eventually able to buy her own place, a farm. And the farm was perfect as her parents would never dare to visit such an icky place.