Jenny is the personal secretary of John, the proprietor of a consultancy firm. Jenny gave birth to a son last year. She now has to leave the office at 5:30 pm sharp (the office hours are 9am to 5:30pm) in order to take care of her son. John always has to work until 9 pm and he does not have the service of Jenny after 5:30 p.m. John is very annoyed and asks terminate the employment with Jenny. John argues that a personal secretary has to work overtime whenever necessary.

What are the legal grounds that Jenny can rely on in making a claim against John in respect of the termination of employment?