It is kind of Adrian's fault that Cassidy is starting to overthink.
While she's not usually that self-conscious, she can't help but pay attention to her perfection of a husband too much. Ever since they made love that night, she realized that he was beyond what she ever expected. She, on the other hand, has confidence that she is beautiful herself, but compared to him, her beauty is probably not that big of a deal.
This is not to say that Cassidy is jealous of Adrian, though.
That's just weird. Rather than that, she only wonders if she's good enough for him.
"Well, since we're already here, we might as well go for a walk," he started again, grabbing her hand and taking her away with him.
She just followed Adrian even when she was still in a bit of a daze. Cassidy should really snap out of it, though.