ha-ri is def a little insecure about her upbringing in comparison to his (partly bc people like min-woo keep bringing up their differences), plus him being her boss, which contributed to her denying her feelings for him bc she didn't think it was a feasible relationship for a person like her to be in. she also generally just seems to worry about how other people view her a lot (her friends, her family, her co-workers, etc.)