Answer:
Revocation
Step-by-step explanation:
Based on the information given She is able to do this because she has the right of REVOCATION which means the right to cancel , terminate, withdraw or bring a contract to an end due to some reason just as the case of Shawna and Philip's in which we were told that Shawna had a second thought on wheither Philip's will have the ability to pay her for the services she is about to rendered to him by deciding to calls Philip in order to withdraw her offer before Philip accepts it.
Therefore Shawna is able to withdraw her offer because she has the right of REVOCATION