Like, Pete and Stan for example. She's clearly very close with them; Stan jumped at the chance to tell her there was a guard position open and was genuinely very excited for her. And unlike other people, they actually listen to her. With how much she means to them, you can't tell me they weren't worried sick about her and so confused as to why she was working with Zhan Tiri. To a lesser extent, maybe Old Lady Crowley. She was practically Cassandra's boss, after all. While she may not have cared all that much, I'm sure that she would've found it a little fishy that Cassandra just suddenly up and betrayed Rapunzel for seemingly no reason.

It's never really stated how close Freidborg and Cass are, but she's also a contender for knowing Cassandra at least well enough that it's not like her to just betray the people she cares about. Cass was important enough to her to be invited to her birthday party. And Cassandra knows Freidborg well enough to know that she never misses a work day. Like Crowley, I have no doubt Freidborg found the whole situation more than a little fishy. And then there's Monty. He seems to have a close relationship with everyone, and Cassandra is certainly no exception. When Rapunzel tells Cassandra that Monty is her hater, Cass's tone seems like "Wait, Uncle Monty actually hates someone???" I get the feeling that when Cap was busy, he probably left little Cass with Monty a few times, so he would know her VERY well.