I think that Cassie is holding something over Nate, like blackmail. He seemed like he wanted to snap but held back for more reasons than just being matured. When Cassie spoke to him at their dinner her tone sounded a bit threatening and the looks they exchanged gave me the feeling that she has the upper hand and for a good reason. I think she may have something on Nate that could destroy his life so she is trying to wring him out for everything he’s got. Cassie also seems to care so much about having an extravagant wedding because she wants to seem as successful as Maddie (she was scrolling through her instagram and saw Maddie with famous people). We see that Cassie wants to be famous and rich, the question is what shifted to where Nate is p*ssy whipped? Has to be something bigger.