When Lisa was caught in the case of plagiarizing Patricia's proposal, she had never met Cicilia. She didn't share in the gossip with the others, nor did she stand up for Lisa. Because of that, Lisa knew what type of person Cicilia was.
The woman prefers to be neutral rather than having to choose one of the 'battling' sides.
If Cicilia openly said that she was on Lisa's side, it was certain that she would be bullied. And knowing her tough and fearless nature, the woman would act as fierce as a beast and fight them back.
Meanwhile, if Cicilia was on their side and joined in sneering at her, Cicilia would have offended her friend. It's no secret that they are close friends. It's funny if she joined the crowd to hate Lisa but then found out that the problem was finally resolved with Lisa proven as innocent. Wouldn't it be awkward to just cling to her again like a normal friend?
Indeed, remaining neutral is the most appropriate way for her.