It's not surprising that someone would have noticed what Larisa was doing.
It is surprising that someone would have considered doing anything about it.
(Doing anything helpful, that is. It would be not at all surprising if some other senior from another enclave noticed and took the apparent opportunity to either murder Larisa and hope to take the empty spot left in her graduation alliance, or else to publicly and dramatically rescue Larisa and accrue the favors recognized for that.)
....Either way, if Cai Xian is carrying out some plot looking more than one or two steps ahead, it's surely not one that he himself came up with, alone. In which case, he has the support of his enclave, and that fact in itself makes it much more costly to antagonize him unnecessarily.
"I appreciate your perceptiveness," Landon says, serious and unsmiling yet somehow still conveying warmth. "Your offer is noted. However, whatever our needs, I - would not be comfortable pointlessly endangering the life of a student from another enclave. So I want to know if, one, you have the support of the Taipei seniors in making this offer, and two, we'd like to have proof of your mal-fighting abilities. Word-of-mouth from someone trusted by Sacramento would suffice, but a demonstration would be better."