Sally is an actress who was offered for a role play of Ophelia by West End, the producers. The salary was meant to be negotiated between the parties. After Sally having accepted the offer, the parties could not agree on the rate of salary.
In the case given above, it can be apparently seen that an agreement between two parties on the bargain was made since offer made by one party was accepted by the other. Having said that one of the initial elements, offer and acceptance, of contract was established. Although, a noticeable point is that there was one condition generated before the bargain was established. In other words, a mutual agreement on an appropriate wage was to be set. This term is considered as a major term because it is significant to the focal aim of the contract. Otherwise, the offeree, Sally could suffer from unfair terms of contract and this is to say that he or she, as an offeror, would be able to provide insufficient/inappropriate amount of wage for their own benefit.
Considering these factors, it could be inferred that Sally has got a right to withdraw the offer since the main condition was not met that she is not satisfied with the rate of salary offered.