I think the fact that he had no doubts about marrying her, while she was having such a hard time thinking about it really threw her off. Getting married is a big deal and the fact that he might not have thought about it as much as she did bothers her to an extent.
He talked about being responsible, but what if she sees him marrying her as an obligation or something he "has to do" rather than something he "wants to do".
I think the fact that he had no doubts about marrying her, while she was having such a hard time thinking about it really threw her off. Getting married is a big deal and the fact that he might not have thought about it as much as she did bothers her to an extent.
He talked about being responsible, but what if she sees him marrying her as an obligation or something he "has to do" rather than something he "wants to do".