@Raydnt
There is no background story of Heroina (yet?), we don't know how she has been growing up, whether she worked hard or not (not like I care/on her side or anything). Let's not make any assumption.
I won't comment on the dense/naive part, because there is a very thin line between naive and stupid. But think for a second: What would happen if the 2 girls switched place? Tia becomes the heroine and Heronia is reincarnated as the villainess? Exactly, high chance they will act to their role, one way or another, because of the obsession.
Both girls share many lovely traits
both are heavily self-righteous, delusional to their own surroundings and ignorant of other people's feelings, i see no difference. Yes, Tia is slightly better because her "motivation" is more... innocent than Heronia, the latter just wanted a harem. But if the pre-set was different, I see no reason Heroine-chan wouldn't win over. Yes, I truly think the prince will get interested in Heroine-chan if he knows her first, it all starts with "this girl is fun" anyway lol.