Elora now understood what Sigma wanted; victory over the boys in the mock battle. It made her feel like she was just nice so she could use her. Then again, if Elora helped her succeed with her plan maybe they could be real friends then, after she has shown she can be reliable. Elora didn't want to waste her only chance at friendship, so she went along with her plan. Besides, she was feeling a bit bad from her crying, so in her mind it wasn't as much a lie as it was an exaggeration. 
The cake also intrigued a bit, but Elora wasn't much of a sweet tooth, and preferred salty treats instead. Serah on the other hand was immediately on board the plan, which made her feel reassured of going along with it.

Elora continued looking miserable, and with a normal voice (which she considered to be really loud), she said: "Good idea. I need some water..."