"I'm not insecure, but I want you to say it," Arthur added and Talia nodded.
For him to say that it is not because he is insecure, it should mean he is a little insecure. Although he is confident, the constant voices screaming at him saying she is marrying him only because he weaseled himself into the Brunton family and conquered the Northern Star, might get to him.
And some even say he pretends to be in love with her for her money. She knew she is someone with a lot of faults but is she that unlovable? If a man fell for her, must it be for her money?
Since he asks her to speak her heart, she knew he's planning to do the same and she didn't even ask him.