This question relates too contract law

Ella, a florist, contracted with Cory to provide delivery services in the local community. Cory discovered his vehicle did not have the equipment to handle the work well, so he asked Ella if another delivery service, Fun Runners, would be acceptable to Ella. After some meetings with Cory and Fun Runners, Ella agreed to the change in delivery services. If Ella has problems with the services of Fun Runners, will she be able to sue Cory or Fun Runners and why?