Does the doctrine of promissory estoppel apply to Fran and Octavia?

Fran finds a shop suitable for her business, and enters into a lease agreement without any troubles. She then advertises online for an assistant to help her in the shop. After interviewing several applicants, she decides on Dante. He is keen to learn and has some experience as an amateur chef. Fran hires Dante as an apprentice chocolatier.

Their written agreement contains a restraint of trade clause. This clause forbids Dante from opening a competitor business in the same area or supplying to the same clients as Fran's business, for one year after leaving the apprenticeship.

Six months into the apprenticeship, Dante feels he has learned all that he can from Fran. He quits.

Two weeks after Dante has gone, Fran finds out that he has approached several of her clients, and has begun providing two of them with similar gourmet chocolates at a lower price.

Fran wants to enforce the restraint of trade clause, but Dante says that the employment contract isn't binding on him.